I hope everyone made it through the lovely weather we experienced Sunday and yesterday. I have submitted grades to the Registrar, they should be visible within a day. The average on the final exam was around 140/200. If you would like to see your final exam, stop by my office. I do not return final exams, but if you'd like to take a look at it you are welcome to do so.
I hope everyone has a great break and I look forward to seeing many of you back in class next semester. Don't forget about Lewis and VSEPR structures, we'll need them to get started in January....
2008-12-16
2008-12-11
Questions...
A few questions came in overnight.....
just like exam #4, are there going to be an "explanation" section about trends in the periodic table or is it going to be "circle which one is bigger/smaller, has higher first ionization energy..."?
Yes, there will be questions where you will be expected to explain your answer.
could you give a brief explanation of endothermic vs exothermic in reaction...i remember i got a couple of those wrong. it seems like it should be straight forward but it's not always!
Endothermic reactions require heat, exothermic reactions liberate heat. The "trick" question here usually involves water freezing. To make water freeze, you must remove heat from the system, so freezing water (or any substance) is an exothermic process, even though it "feels cold" if you were to hold it in your hand.
Other questions, let me know. See you in a few hours...
just like exam #4, are there going to be an "explanation" section about trends in the periodic table or is it going to be "circle which one is bigger/smaller, has higher first ionization energy..."?
Yes, there will be questions where you will be expected to explain your answer.
could you give a brief explanation of endothermic vs exothermic in reaction...i remember i got a couple of those wrong. it seems like it should be straight forward but it's not always!
Endothermic reactions require heat, exothermic reactions liberate heat. The "trick" question here usually involves water freezing. To make water freeze, you must remove heat from the system, so freezing water (or any substance) is an exothermic process, even though it "feels cold" if you were to hold it in your hand.
Other questions, let me know. See you in a few hours...
2008-12-10
Tomorrow...
I will be in my office by 8am tomorrow, if you have any last minute questions feel free to stop by.
The 1-Question Final Exam
A few people have asked for the answer to this question, so......
325.0mL of 0.825M sodium carbonate solution reacts with 11.348L of hydrogen chloride gas at 1.082atm pressure and 17.28°C to produce carbon dioxide gas, liquid water, and sodium chloride. How many grams of carbon dioxide gas can be produced by this reaction? If all of the sodium chloride that can be produced by this reaction is dissolved in enough water to make 450.0mL of solution, what will be the concentration of sodium chloride in the solution?
First, we need a balanced chemical equation. This is a gas forming reaction.
Na2CO3(aq) + 2 HCl(g) --> H2O(l) + CO2(g) + 2 NaCl(aq)
{Remember, carbonic acid spontaneously decomposes to water and carbon dioxide gas.}
Now we've got a couple stoichiometry problems...
(0.825 mols Na2CO3/L sol'n)(0.3250L sol'n)(1mol CO2(g)/1mol Na2CO3(aq))(44.009 g CO2/mol CO2 ) = 11.8g CO2(g)
((1.082atm)(11.348L HCl(g))/(0.08206 L.atm/mol.K)(290.43K))(1mol CO2(g)/2mol HCl(g))(44.009 g CO2/mol CO2 ) = 11.3g CO2(g)
Since the HCl(g) produces less product, it must be the limiting reagent, so this reaction can produce 11.3g of CO2(g).
Knowing that HCl(g) is the limiting reagent, we can calculate the amount of NaCl produced by this reaction:
((1.082atm)(11.348L HCl(g))/(0.08206 L.atm/mol.K)(290.43K))(2mol NaCl(aq)/2mol HCl(g)) = 0.515197 mols NaCl(aq) {NOTE: yes, this is too many sig figs, but it's the middle of a problem so I do not want to round off to the correct number of sig figs yet...}
If this amount of NaCl is dissolved in enough water to make 450.0mL of solution, the concentration is:
0.515197mols NaCl / 0.4500L sol'n = 1.145M NaCl(aq)
325.0mL of 0.825M sodium carbonate solution reacts with 11.348L of hydrogen chloride gas at 1.082atm pressure and 17.28°C to produce carbon dioxide gas, liquid water, and sodium chloride. How many grams of carbon dioxide gas can be produced by this reaction? If all of the sodium chloride that can be produced by this reaction is dissolved in enough water to make 450.0mL of solution, what will be the concentration of sodium chloride in the solution?
First, we need a balanced chemical equation. This is a gas forming reaction.
Na2CO3(aq) + 2 HCl(g) --> H2O(l) + CO2(g) + 2 NaCl(aq)
{Remember, carbonic acid spontaneously decomposes to water and carbon dioxide gas.}
Now we've got a couple stoichiometry problems...
(0.825 mols Na2CO3/L sol'n)(0.3250L sol'n)(1mol CO2(g)/1mol Na2CO3(aq))(44.009 g CO2/mol CO2 ) = 11.8g CO2(g)
((1.082atm)(11.348L HCl(g))/(0.08206 L.atm/mol.K)(290.43K))(1mol CO2(g)/2mol HCl(g))(44.009 g CO2/mol CO2 ) = 11.3g CO2(g)
Since the HCl(g) produces less product, it must be the limiting reagent, so this reaction can produce 11.3g of CO2(g).
Knowing that HCl(g) is the limiting reagent, we can calculate the amount of NaCl produced by this reaction:
((1.082atm)(11.348L HCl(g))/(0.08206 L.atm/mol.K)(290.43K))(2mol NaCl(aq)/2mol HCl(g)) = 0.515197 mols NaCl(aq) {NOTE: yes, this is too many sig figs, but it's the middle of a problem so I do not want to round off to the correct number of sig figs yet...}
If this amount of NaCl is dissolved in enough water to make 450.0mL of solution, the concentration is:
0.515197mols NaCl / 0.4500L sol'n = 1.145M NaCl(aq)
2008-12-08
Last day....
Exam 4 was returned today, average was ~110/150. Based on your 3 highest exam scores and Mastering Chemistry, I would estimate the current grade cutoffs at: 90.% = A, 80.% = B, 68% = C, 55% = D. Those cutoffs may shift around a little once the final exam scores are entered, but they shouldn't move significantly.
Don't forget, as stated in the syllabus, if you do not take the final exam, you fail the course regardless of previous performance.
As I mentioned in class, I have been tempted in the past to give a 1-question final exam. I do not actually do this because it would be exceptionally stressful for both you and me, but if I were to give a 1-question final exam, the question would probably look something like this:
325.0mL of 0.825M sodium carbonate solution reacts with 11.348L of hydrogen chloride gas at 1.082atm pressure and 17.28°C to produce carbon dioxide gas, liquid water, and sodium chloride. How many grams of carbon dioxide gas can be produced by this reaction? If all of the sodium chloride that can be produced by this reaction is dissolved in enough water to make 450.0mL of solution, what will be the concentration of sodium chloride in the solution?
If you have any other questions, stop by my office or email me. I will post answers to any emailed questions to the class blog. Good luck with your preparation and I'll see you on Thursday (or sooner...).
Don't forget, as stated in the syllabus, if you do not take the final exam, you fail the course regardless of previous performance.
As I mentioned in class, I have been tempted in the past to give a 1-question final exam. I do not actually do this because it would be exceptionally stressful for both you and me, but if I were to give a 1-question final exam, the question would probably look something like this:
325.0mL of 0.825M sodium carbonate solution reacts with 11.348L of hydrogen chloride gas at 1.082atm pressure and 17.28°C to produce carbon dioxide gas, liquid water, and sodium chloride. How many grams of carbon dioxide gas can be produced by this reaction? If all of the sodium chloride that can be produced by this reaction is dissolved in enough water to make 450.0mL of solution, what will be the concentration of sodium chloride in the solution?
If you have any other questions, stop by my office or email me. I will post answers to any emailed questions to the class blog. Good luck with your preparation and I'll see you on Thursday (or sooner...).
2008-12-04
Exam questions....
A couple questions have come in for tomorrow's exam.....
Just wondering if any like light waves, Hz questions from chapter seven are
going to be on the test..?!
That info is fair game for the exam...BUT think about how much time we spent on it. We spent maybe a day or two on that info, but we spent WEEKS talking about electron configurations, periodic trends, Lewis structures, VSEPR... The exam will reflect this, if there is a question about light, it will probably be a small question...
could you please explain how to determine which charges are best for elements?? i'm having a hard time understanding just how to find the ones your looking for, could you explain in an email??
Relatively stable ions are formed by relatively stable electron configurations. Electrons are relatively stable when: 1)all the shells are full; 2)all the subshells are full; 3)the subshells are half full. Let's look at a couple examples.
1) Sodium forms a relatively stable ion with a +1 charge because when a sodium atom loses an electron it has the same electron configuration as neon, which has full shells.
1s22s22p63s1 --> 22s22p6
2) Zinc forms a relatively stable ion with a +2 charge because when a zinc atom loses two electrons all of the occupied subshells are full.
[Ar]4s23d10 --> [Ar]3d10
3) Manganese forms a relatively stable ion with a +2 charge because when a manganese atom loses 2 electrons all of the occupied subshells are either full or half full.
[Ar]4s23d5 --> [Ar]3d5
If you're looking for stable ions, write out the electron configuration for the neutral atom and look at how many electrons you have to add or remove to get to full or half full subshells.
I'll be off-line until tomorrow morning, if you have other questions either drop me an email or post a comment to the blog and I'll answer them as soon as I get in. If you notice a question posted to the blog and would like to help out your classmates, feel free to post a follow-up comment to answer the question. See you all tomorrow.
Just wondering if any like light waves, Hz questions from chapter seven are
going to be on the test..?!
That info is fair game for the exam...BUT think about how much time we spent on it. We spent maybe a day or two on that info, but we spent WEEKS talking about electron configurations, periodic trends, Lewis structures, VSEPR... The exam will reflect this, if there is a question about light, it will probably be a small question...
could you please explain how to determine which charges are best for elements?? i'm having a hard time understanding just how to find the ones your looking for, could you explain in an email??
Relatively stable ions are formed by relatively stable electron configurations. Electrons are relatively stable when: 1)all the shells are full; 2)all the subshells are full; 3)the subshells are half full. Let's look at a couple examples.
1) Sodium forms a relatively stable ion with a +1 charge because when a sodium atom loses an electron it has the same electron configuration as neon, which has full shells.
1s22s22p63s1 --> 22s22p6
2) Zinc forms a relatively stable ion with a +2 charge because when a zinc atom loses two electrons all of the occupied subshells are full.
[Ar]4s23d10 --> [Ar]3d10
3) Manganese forms a relatively stable ion with a +2 charge because when a manganese atom loses 2 electrons all of the occupied subshells are either full or half full.
[Ar]4s23d5 --> [Ar]3d5
If you're looking for stable ions, write out the electron configuration for the neutral atom and look at how many electrons you have to add or remove to get to full or half full subshells.
I'll be off-line until tomorrow morning, if you have other questions either drop me an email or post a comment to the blog and I'll answer them as soon as I get in. If you notice a question posted to the blog and would like to help out your classmates, feel free to post a follow-up comment to answer the question. See you all tomorrow.
2008-12-03
Ready for the exam?
Today we finished up our discussion of the MO diagram of oxygen and went through a few questions in review for the exam on Friday. If you have any other questions, let me know, I'll post answers to the blog.
Don't forget the Chem Club meeting tonight and your Mastering Chemistry assignment.
Don't forget the Chem Club meeting tonight and your Mastering Chemistry assignment.
2008-12-01
Chem Club meeting this week
Don't forget that the Chem Club will be meeting this Wednesday, SL104, 7pm.
VB, Hybrid orbitals, LCAO-MO
Today we looked at how hybrid atomic orbitals can be used to understand the shapes and angles predicted by VSEPR. We used this idea of adding and subtracting orbitals to look at molecules and took an initial look at some molecular orbital diagrams for "simple" diatomics.
There is a new Mastering Chemistry assignment posted, due Thursday. This is the last MC assignment for the semester.
For those of you who will be continuing on in Chem 210, keep your book! We will be using the same book in Chem 210. If you are continuing in my class, you will also continue to use Mastering Chemistry. You should be able to continue using the same MC account, they're valid for at least a year (maybe 18 months?). If you are moving over to Dr. Edvenson's class, I don't know if you will be using MC.
There is a new Mastering Chemistry assignment posted, due Thursday. This is the last MC assignment for the semester.
For those of you who will be continuing on in Chem 210, keep your book! We will be using the same book in Chem 210. If you are continuing in my class, you will also continue to use Mastering Chemistry. You should be able to continue using the same MC account, they're valid for at least a year (maybe 18 months?). If you are moving over to Dr. Edvenson's class, I don't know if you will be using MC.
2008-11-24
Molecular polarity
Today we talked about how VSEPR structures can be used to predict macroscale physical properties. The biggest property to look for is molecular polarity. If a molecule or ion has polar bonds that do not all cancel themselves out, the molecule or ion is polar. This influences a number of different properties from melting/boiling point to solubility.
Keep on practicing those Lewis and VSEPR structures. Maybe during your Thanksgiving dinner you could use peas and mashed potatoes to build a series of Lewis structures, then construct VSEPR models using marshmallows and pretzels. Teach your younger siblings and cousins about the repulsive interactions between electrons and the difference between LP-LP, LP-BP and BP-BP interactions. Don't just have a Thanksgiving, make this year a Thinksgiving!
Either that, or just eat too much, visit with family and friends, and relax a bit so you're ready to take on the last couple weeks of the semester.
Have a great weekend, and I'll see you all on Monday.
Keep on practicing those Lewis and VSEPR structures. Maybe during your Thanksgiving dinner you could use peas and mashed potatoes to build a series of Lewis structures, then construct VSEPR models using marshmallows and pretzels. Teach your younger siblings and cousins about the repulsive interactions between electrons and the difference between LP-LP, LP-BP and BP-BP interactions. Don't just have a Thanksgiving, make this year a Thinksgiving!
Either that, or just eat too much, visit with family and friends, and relax a bit so you're ready to take on the last couple weeks of the semester.
Have a great weekend, and I'll see you all on Monday.
2008-11-21
Drawing VSEPR and those troublesome lone pairs...
Today we talked about drawing VSEPR structures and the shapes that result from structures that contain lone pairs. The shapes and angles are all a result of lone pairs (LPs) being "bigger" than bonding pairs (BPs), meaning that LP-LP interactions are more intense than LP-BP interactions which are more intense than BP-BP interactions.
Don't forget about your current Mastering Chemistry assignments, Assignment 18 is due Saturday, Assignment 19 is due Tuesday.
Again, for students in all of my lab sections, your Iron Ore hand in is due by noon next Tuesday, November 25th.
Have a good weekend, I'll see you all on Monday.
Don't forget about your current Mastering Chemistry assignments, Assignment 18 is due Saturday, Assignment 19 is due Tuesday.
Again, for students in all of my lab sections, your Iron Ore hand in is due by noon next Tuesday, November 25th.
Have a good weekend, I'll see you all on Monday.
"Other" elements in Mastering Chemistry
A number of people have run into the problem of entering elements other than those listed in the pop-down menu when drawing Lewis structures in Mastering Chemistry. If you need an unlisted element (like, perhaps, Si...), you can draw a carbon (or any other element) then double click on the "C". At that point, you should be able to type in the symbol of whatever element you need. This actually works for any element, so if you want to draw your entire skeleton structure in using the default element (carbon) and then double click your way through to change elements to O or F or whatever else, you can do that.
2008-11-19
VSEPR
Today was our first big VSEPR day. We went over the electronic geometries associated with 2-6 regions of electron density (2 R.E.D. = linear; 3 R.E.D. = trigonal planar; 4 R.E.D. = tetrahedral; 5 R.E.D. = trigonal bipyramidal; 6 R.E.D. = octahedral) including the bond angles predicted by each of these geometries. This is a pretty big topic/concept, and the only way you'll get good at is by looking at and working through examples. The best thing you can do is look back over your class notes and study notes and every time you find a molecule, draw out a Lewis structure and assign a VSEPR electronic geometry. We'll be spending at least another day on this (probably 2 or 3).
For all of my lab students, your Fe ore hand in is due by noon next Tuesday. If you are in one of Dr. Marasinghe's labs or Dr. Edvenson's lab, check with your instructor for deadlines on this and all assignments.
For all of my lab students, your Fe ore hand in is due by noon next Tuesday. If you are in one of Dr. Marasinghe's labs or Dr. Edvenson's lab, check with your instructor for deadlines on this and all assignments.
2008-11-17
Wrap up Chapter 9
We cleaned up a few topics today including bond length and strength trends, using bond strengths to estimate {delta}H for a reaction, and using the Bond-Type Triangle to predict the type of bonding in binary compounds. We also just barely started talking about VSEPR, we'll probably spend the rest of the week and next week on VSEPR.
Drop-in tutoring/help is available in HA405 at the following times:
Monday 3-4:30pm {Amber Goraczkowski}
Tuesday 11:45am-1pm {Eric Berget}
Wednesday 2-3pm {Joelle Rolfs}
There's a new MC posted, this one has a few more questions than the last couple, so don't wait to get started on it.
Drop-in tutoring/help is available in HA405 at the following times:
Monday 3-4:30pm {Amber Goraczkowski}
Tuesday 11:45am-1pm {Eric Berget}
Wednesday 2-3pm {Joelle Rolfs}
There's a new MC posted, this one has a few more questions than the last couple, so don't wait to get started on it.
2008-11-14
Friday, Friday, Friday....
Today we looked at some more examples of resonance and used bond order to describe bonds that are resonance averaged.
The Chem Club is organizing drop-in tutoring for Gen Chem. These will be people who were successful in Gen Chem and are offering their assistance to you. Drop-in tutoring is informal, there is no set "lesson" and you don't need to sign up or register, just stop in if you have questions. For now, sessions will be held in HA405 on Mondays at 3-4:30pm {Amber Goraczkowski} and Tuesdays 11:45am-1pm {Eric Berget}. More times may become available, I'll post any information I get here on the blog.
There's a new MC, due Tuesday.
Have a good weekend, I'll see you all Monday.
The Chem Club is organizing drop-in tutoring for Gen Chem. These will be people who were successful in Gen Chem and are offering their assistance to you. Drop-in tutoring is informal, there is no set "lesson" and you don't need to sign up or register, just stop in if you have questions. For now, sessions will be held in HA405 on Mondays at 3-4:30pm {Amber Goraczkowski} and Tuesdays 11:45am-1pm {Eric Berget}. More times may become available, I'll post any information I get here on the blog.
There's a new MC, due Tuesday.
Have a good weekend, I'll see you all Monday.
2008-11-12
Lewis structures
Today we worked through a couple examples of Lewis structures and looked at the concept of formal charge as a way to decide whether a Lewis structure is "good". We also looked at resonance structures and talked about electronegativity as a way to decide how molecules and polyatomic ions should be assembled. Lewis structures are extremely useful tools and require a bit of practice, so don't wait to practice them.
A new MC assignment is posted.
A new MC assignment is posted.
2008-11-10
Atom/Ion size and bond types
Today we wrapped up trends in ionic radius compared to neutral atoms and started talking about different types of chemical bonding. We just started looking at Lewis structures as a tool which will help us understand covalent bonding, and we'll continue with more Lewis structures throughout the rest of this week. In all cases, we're looking at how atomic/periodic structure can help us predict macroscopic behavior and properties.
2008-11-07
More electron configs and periodic trends
Today we talked about a couple more periodic trends and how they relate to the electron configuration of the atoms and/or ions involved. We talked about magnetism, ionization energy and electron affinity. We also looked at a problem set in class that should show us the trend in ionic size/radius for either cations or anions. It didn't seem like most people made it through the whole problem set in class, so be sure to take a look at it over the weekend and we'll wrap that one up in a couple minutes at the beginning of class on Monday.
There's a new Mastering Chemistry posted, due Tuesday. Don't forget the current MC assignment, due tonight.
Don't forget the "Diggin for a Cure" volleyball game tonight, the team also plays tomorrow afternoon. If any other teams, groups, or organizations would like me to mention their events on the class blog, let me know. I'm always interested to know what people in class are involved in.
There's a new Mastering Chemistry posted, due Tuesday. Don't forget the current MC assignment, due tonight.
Don't forget the "Diggin for a Cure" volleyball game tonight, the team also plays tomorrow afternoon. If any other teams, groups, or organizations would like me to mention their events on the class blog, let me know. I'm always interested to know what people in class are involved in.
2008-11-05
Electron configs and periodic properties
Today we discussed quantized energy levels and looked at a few more electron configurations. We also began to look at how electron configurations could be used to predict the properties of elements. We looked at atomic size/radius, we'll continue to look at other properties over the next couple days.
Chem Club meeting TONIGHT at 7:30pm in SL104.
I'll also make another specific pitch here for SI. The tools we're using right now (quantum numbers, electron configurations, etc) become much easier to work with if you practice, practice practice them. SI is an excellent opportunity for you to practice some of these things in an environment where you can help others and they can help you. Don't wait until the week before the next exam to work on these things.
Finally, this Friday night the MSUM volleyball team will be "Diggin for a Cure". The game starts at 7pm and the Dragons will be wiping the floor with St. Cloud State. Wear purple to show your support, T-shirts will be on sale ($10) at the game or in the MSUM Athletics Office. Come out to Nemzek to cheer on the team and support this worthy cause.
Chem Club meeting TONIGHT at 7:30pm in SL104.
I'll also make another specific pitch here for SI. The tools we're using right now (quantum numbers, electron configurations, etc) become much easier to work with if you practice, practice practice them. SI is an excellent opportunity for you to practice some of these things in an environment where you can help others and they can help you. Don't wait until the week before the next exam to work on these things.
Finally, this Friday night the MSUM volleyball team will be "Diggin for a Cure". The game starts at 7pm and the Dragons will be wiping the floor with St. Cloud State. Wear purple to show your support, T-shirts will be on sale ($10) at the game or in the MSUM Athletics Office. Come out to Nemzek to cheer on the team and support this worthy cause.
2008-11-04
From light waves to atomic orbitals
Sorry I didn't get this up sooner, something came up yesterday.
Monday in class we transitioned from our discussion of light and waves to the behavior of electrons. This is partially explained by deBroglie's relationship which describes the wave-like character of moving electrons. Since chemistry is all about electrons, we needed a system to address individual electrons in an atom so we talked about quantum numbers and began to look at how we could use a shorthand version of quantum numbers (called electron configurations) to begin to predict properties of elements. We'll pick up there on Wednesday.
There is a new Mastering Chemistry assignment posted, due Friday. The monthly Chem Club meeting is also being held this week, Wednesday night at 7:30pm in SL104.
Monday in class we transitioned from our discussion of light and waves to the behavior of electrons. This is partially explained by deBroglie's relationship which describes the wave-like character of moving electrons. Since chemistry is all about electrons, we needed a system to address individual electrons in an atom so we talked about quantum numbers and began to look at how we could use a shorthand version of quantum numbers (called electron configurations) to begin to predict properties of elements. We'll pick up there on Wednesday.
There is a new Mastering Chemistry assignment posted, due Friday. The monthly Chem Club meeting is also being held this week, Wednesday night at 7:30pm in SL104.
2008-11-01
The nature of light....
Friday in class exams were returned. The average was up a bit (around 120/150) on the exam, and now that we have 3 exams in the books we can start making a little more informed projection of course grades. Given the current scores and distribution, if I drop everyone's lowest exam score it looks like the syllabus grade cutoffs are appropriate: 90.0% for A's, 80.0% for B's, 70.0% for C's, 60.0% for D's. I typically use +/- grades, so if you're are the very top or bottom of one of those ranges you will likely see a + or -. We still have 1 regular 150pt exam and a 200pt final exam and a few more Mastering Chemistry assignments, so there are quite a few points still out there to be earned (or lost). As a point of reference, the class is worth 750pts total. Add up your 2 highest exam scores and your current percentage in Mastering Chemistry to see how many more points you have to earn to reach your goal grade. An A will probably require >675pts, B>600pts, C>525pts, D>450pts.
We also started talking about the nature of light as described in Chapter 7. I didn't go over every little detail, your textbook does a fine job of that. We'll put that discussion of light into an atomic context Monday in class.
Have a good weekend and don't forget to set your clocks back on Saturday night/Sunday morning.
We also started talking about the nature of light as described in Chapter 7. I didn't go over every little detail, your textbook does a fine job of that. We'll put that discussion of light into an atomic context Monday in class.
Have a good weekend and don't forget to set your clocks back on Saturday night/Sunday morning.
2008-10-28
More exam questions....
A number of people are still struggling with some of these ΔH manipulations, so let's look at a a bare-bones example. For the reaction A -> B, you have determined that ΔH = +10kJ/mol. If this is true, what's ΔH for the reaction B -> A? The difference in enthalpy between substance "A" and substance "B" is 10kJ/mol, the sign just tells you which is higher (or lower), therefore, ΔH for the reaction B -> A is the same magnitude but in the opposite direction. Similarly, what about the reaction 2A -> 2B? This reaction represents twice as much "action" as the original A -> B, so the energy required (it's endothermic) must be twice as much as the original. Summarizing:
A -> B ΔH=+10kJ/mol
B -> A ΔH=-10kJ/mol
2A -> 2B ΔH=+20kJ/mol
5B -> 5A ΔH=-50kJ/mol
Another question from a previous exam, I've copied the answer key below:
13. The specific heat capacity of gold is 0.128J/g•ÂºC and the specific heat capacity of iron is 0.449
J/g•ÂºC. You have heated a 51.294g block of iron to 49.318ºC and placed it on a gold block at
21.516ºC. When the system reaches thermal equilibrium, the temperature of the gold and
iron blocks are 34.468ºC. If the system is perfectly insulated, what was the mass of the gold
block in grams? (20pts each)
The assumption that the system is perfectly insulated implies that all of the energy lost by the iron block is
transferred to the gold block. Finding the energy lost by the iron block:
Eiron = (0.449 J/g•ÂºC)(51.294g Fe)(14.850ºC)
And the energy gained by the gold block:
Egold = (0.128 J/g•ÂºC)(x g Au)(12.952ºC)
Setting these energies equal:
(0.449 J/g•ÂºC)(51.294g Fe)(14.850ºC) = (0.128 J/g•ÂºC)(x g Au)(12.952ºC)
x = 206g Au
The question came up because this problem might appear to be missing a couple negative signs. Well, it's sort of missing a couple negative signs, so let me clarify (hopefully). The block of iron starts out hot and transfers heat to the gold block. That means that the temperature change for iron should be negative (34.468-49.318 = -14.850), which will give a negative value of Eiron. But look at how the answer is worded. By stating that the energy is lost by the iron block, the answer is implying a negative sign. In this case, the way I worded the answer takes care of the positive and negative signs because I was looking at the quantity of energy independent of the direction that energy was being transferred. If you leave the negatives in when you calculate Eiron, then you will need to include an additional negative sign when you set Eiron equal to Egold.
A -> B ΔH=+10kJ/mol
B -> A ΔH=-10kJ/mol
2A -> 2B ΔH=+20kJ/mol
5B -> 5A ΔH=-50kJ/mol
Another question from a previous exam, I've copied the answer key below:
13. The specific heat capacity of gold is 0.128J/g•ÂºC and the specific heat capacity of iron is 0.449
J/g•ÂºC. You have heated a 51.294g block of iron to 49.318ºC and placed it on a gold block at
21.516ºC. When the system reaches thermal equilibrium, the temperature of the gold and
iron blocks are 34.468ºC. If the system is perfectly insulated, what was the mass of the gold
block in grams? (20pts each)
The assumption that the system is perfectly insulated implies that all of the energy lost by the iron block is
transferred to the gold block. Finding the energy lost by the iron block:
Eiron = (0.449 J/g•ÂºC)(51.294g Fe)(14.850ºC)
And the energy gained by the gold block:
Egold = (0.128 J/g•ÂºC)(x g Au)(12.952ºC)
Setting these energies equal:
(0.449 J/g•ÂºC)(51.294g Fe)(14.850ºC) = (0.128 J/g•ÂºC)(x g Au)(12.952ºC)
x = 206g Au
The question came up because this problem might appear to be missing a couple negative signs. Well, it's sort of missing a couple negative signs, so let me clarify (hopefully). The block of iron starts out hot and transfers heat to the gold block. That means that the temperature change for iron should be negative (34.468-49.318 = -14.850), which will give a negative value of Eiron. But look at how the answer is worded. By stating that the energy is lost by the iron block, the answer is implying a negative sign. In this case, the way I worded the answer takes care of the positive and negative signs because I was looking at the quantity of energy independent of the direction that energy was being transferred. If you leave the negatives in when you calculate Eiron, then you will need to include an additional negative sign when you set Eiron equal to Egold.
Exam prep questions.....
A couple questions have come in on email:
How do we do a problem like this? i got it from the spring 2008 exam 3a.
You have determined that ΔHºreaction for the following reaction is –311.2kJ/mol.
3 Ca(OH)2(s) + 2 H3PO4(s) -> Ca3(PO4)2(s) + 6 H2O(l)
What is ΔHºreaction for the reaction:
2 Ca3(PO4)2(s) + 12 H2O(l)-> 6 Ca(OH)2(s) + 4 H3PO4(s)
a. 622.4 kJ/mol
b. 311.2 kJ/mol
c. 155.6 kJ/mol
d. -311.2 kJ/mol
e. -622.4 kJ/mol
This question is all about how the value of ΔHºreaction changes as a reaction is modified. The "new" reaction is the reverse of the original reaction, so the "new" process must be endothermic rather than exothermic (change the sign of ΔHºreaction). The "new" reaction is also balanced as a multiple of the first, so if 2x as much reaction occurs, then 2x the heat is required. The correct answer is "a".
Yes, I expect you to be able to draw these. "Qualitatively correct" means I'm not looking for perfectly measured jumps and drops, but if a step in a reaction is 20kJ/mol exothermic it should look significantly larger than a step that's 2 kJ/mol exothermic, and both of them should be steps down. Your text doesn't always exactly call them reaction coordinate diagrams, but the figures on p. 242, 260, and 264 are all reaction coordinate diagrams. Although they're formatted a little differently than the way I typically draw them, these diagrams are conveying the same type of information. For those of you who will be taking Chem 210, some of the concepts we talk about in the second semester will be significantly easier to visualize if you start thinking about reactions as they appear/occur in a reaction coordinate diagram.
Keep the questions coming, I will post answers to the blog as soon as I can.
How do we do a problem like this? i got it from the spring 2008 exam 3a.
You have determined that ΔHºreaction for the following reaction is –311.2kJ/mol.
3 Ca(OH)2(s) + 2 H3PO4(s) -> Ca3(PO4)2(s) + 6 H2O(l)
What is ΔHºreaction for the reaction:
2 Ca3(PO4)2(s) + 12 H2O(l)-> 6 Ca(OH)2(s) + 4 H3PO4(s)
a. 622.4 kJ/mol
b. 311.2 kJ/mol
c. 155.6 kJ/mol
d. -311.2 kJ/mol
e. -622.4 kJ/mol
This question is all about how the value of ΔHºreaction changes as a reaction is modified. The "new" reaction is the reverse of the original reaction, so the "new" process must be endothermic rather than exothermic (change the sign of ΔHºreaction). The "new" reaction is also balanced as a multiple of the first, so if 2x as much reaction occurs, then 2x the heat is required. The correct answer is "a".
I was doing some practice exams from previous years and are we
going to have to know how to do a qualitatively correct reaction coordinate
diagram for a stepwise process?
Yes, I expect you to be able to draw these. "Qualitatively correct" means I'm not looking for perfectly measured jumps and drops, but if a step in a reaction is 20kJ/mol exothermic it should look significantly larger than a step that's 2 kJ/mol exothermic, and both of them should be steps down. Your text doesn't always exactly call them reaction coordinate diagrams, but the figures on p. 242, 260, and 264 are all reaction coordinate diagrams. Although they're formatted a little differently than the way I typically draw them, these diagrams are conveying the same type of information. For those of you who will be taking Chem 210, some of the concepts we talk about in the second semester will be significantly easier to visualize if you start thinking about reactions as they appear/occur in a reaction coordinate diagram.
Keep the questions coming, I will post answers to the blog as soon as I can.
2008-10-27
Almost exam time....
Today we went over a few problems that people asked about in preparation for the exam on Wednesday. If you have questions, let me know and I will post answers on the blog.
If you're looking for sample exams, last fall and spring Exam #3 are probably a good place to start. There may be a couple questions on those exams from Chapter 7, so if a question seems beyond what we've covered in class it probably is. Any of the previous years' Exam #3 will have Thermodynamics, heat capacity and enthalpy problems, so check those out as well.
Test Review SI session will be Tuesday at 1:30 in LO 84
Good luck in your test prep and I'll see you all Wednesday if not sooner.
If you're looking for sample exams, last fall and spring Exam #3 are probably a good place to start. There may be a couple questions on those exams from Chapter 7, so if a question seems beyond what we've covered in class it probably is. Any of the previous years' Exam #3 will have Thermodynamics, heat capacity and enthalpy problems, so check those out as well.
Test Review SI session will be Tuesday at 1:30 in LO 84
Good luck in your test prep and I'll see you all Wednesday if not sooner.
2008-10-25
Net ionic equation and combustion reactions
Friday in class we examined how the enthalpy of a reaction can be calculated by using the net ionic equation rather than the full equation, with the result being the same in either case. This is because the net ionic equation is describing the chemistry that occurs without all the "fluff" of spectator ions. We also worked through an activity looking at the enthalpy of combustion for a variety of fuels. By critically evaluating the numerical data, we can determine which fuel is the "best" based upon whatever we consider most important (energy content, storage capacity, transportation issues)
2008-10-22
Coupled enthalpy problems and Hess' Law
Looks like I missed posting after Monday's class. Oop.
We're elbow-deep in enthalpy at this point, today we worked through another couple problems in which we calculated the enthalpy of reaction, and used the enthalpy/heat/energy liberated by a reaction to heat up a block of granite in a heat capacity problem. We also worked through an example of a multi-step reaction and the realtionship between the enthalpy of each step and the overall enthalpy of the net reaction. This is Hess' Law, and is basically an example of how state functions work: the path doesn't matter, just the starting and ending points.
A new Mastering Chemistry is posted, due Monday. Don't wait until the last minute, our next exam is next Wednesday. As I mentioned in class today, Exam #3 will only cover through Chapter 6, we'll roll Chapter 7 into the next exam.
We're elbow-deep in enthalpy at this point, today we worked through another couple problems in which we calculated the enthalpy of reaction, and used the enthalpy/heat/energy liberated by a reaction to heat up a block of granite in a heat capacity problem. We also worked through an example of a multi-step reaction and the realtionship between the enthalpy of each step and the overall enthalpy of the net reaction. This is Hess' Law, and is basically an example of how state functions work: the path doesn't matter, just the starting and ending points.
A new Mastering Chemistry is posted, due Monday. Don't wait until the last minute, our next exam is next Wednesday. As I mentioned in class today, Exam #3 will only cover through Chapter 6, we'll roll Chapter 7 into the next exam.
2008-10-17
Coupled systems and heat of reaction
Today we worked through a coupled systems problem in which a warm block of lead transferred energy to a cooler block of silver. In working through the algebra, I made an error somewhere and came up with the wrong answer, so let's try to correct it here. The set-up was OK, so we got to the following equation:
(0.128 J/g.degC)(17.89g)(Tfinal-42.73degC) = -(0.235 J/g.degC)(23.13g)(Tfinal-15.42degC)
This is set up correctly, now we have to work through the algebra:
(Tfinal-42.73degC) = -{(0.235 J/g.degC)(23.13g)}/{(0.128 J/g.degC)(17.89g)}(Tfinal-15.42degC)
Turning the great big ugly fraction into a number, we get:
(Tfinal-42.73degC) = -(2.3737)(Tfinal-15.42degC)
Distributing the -2.3737:
(Tfinal-42.73degC) = -(2.3737Tfinal)+(2.3737)(15.42degC)
Moving the Tfinal terms to one side and the numerical terms to the other:
Tfinal + 2.3737Tfinal = (2.3737)(15.42degC) + 42.73degC
Factoring out Tfinal and solving:
Tfinal = {(2.3737)(15.42degC) + 42.73degC}/{1 + 2.3737} = 23.5degC
There is a new Mastering Chemistry posted, due Tuesday. Have a great weekend.
(0.128 J/g.degC)(17.89g)(Tfinal-42.73degC) = -(0.235 J/g.degC)(23.13g)(Tfinal-15.42degC)
This is set up correctly, now we have to work through the algebra:
(Tfinal-42.73degC) = -{(0.235 J/g.degC)(23.13g)}/{(0.128 J/g.degC)(17.89g)}(Tfinal-15.42degC)
Turning the great big ugly fraction into a number, we get:
(Tfinal-42.73degC) = -(2.3737)(Tfinal-15.42degC)
Distributing the -2.3737:
(Tfinal-42.73degC) = -(2.3737Tfinal)+(2.3737)(15.42degC)
Moving the Tfinal terms to one side and the numerical terms to the other:
Tfinal + 2.3737Tfinal = (2.3737)(15.42degC) + 42.73degC
Factoring out Tfinal and solving:
Tfinal = {(2.3737)(15.42degC) + 42.73degC}/{1 + 2.3737} = 23.5degC
There is a new Mastering Chemistry posted, due Tuesday. Have a great weekend.
2008-10-15
Internal energy and heat capacity
Today we talked about internal energy and how keeping track of the work done on or by the system and the heat transferred into or out of the system can help us follow the change in internal energy of a system. In order to relate heat transfer and temperature change, we explored the concept of heat capacity, especially the more generally applicable specific heat capacity and molar hear capacity. We'll take a closer look at some heat capacity problems on Friday and begin to look at the factors that influence heat transfer in chemical reactions.
2008-10-10
Exam returned and Thermodynamics
Today in class exams were returned. If you were not in class, I will bring exams with me next Wednesday. The average was a little lower than last time. I also took a closer look at Mastering Chemistry scores and there are quite a few people who are just not doing Mastering Chemistry assignments. Try to keep up on these, MC is around 13% of your grade.
For anyone in my lab sections, hand-ins are due next Wednesday by 12:30pm for all of my sections (Tuesday 9am, Wednesday 11:30am, Thursday 9am). Chem 150L will not meet next week due to the Fall Breather.
Have a great weekend and I'll see you all on Wednesday.
For anyone in my lab sections, hand-ins are due next Wednesday by 12:30pm for all of my sections (Tuesday 9am, Wednesday 11:30am, Thursday 9am). Chem 150L will not meet next week due to the Fall Breather.
Have a great weekend and I'll see you all on Wednesday.
2008-10-06
Acid strength
One of the multiple choice questions brings up the idea of strong vs. weak acids and bases:
Which of the following is the strongest acid?
a.KOH (aq)
b.HClO4 (aq)
c.HC2H3O2 (aq)
d.H20 (aq)
e.NH3 (aq)
Strong acids (and bases) are those which ionize/dissolve completely when added to water. Let's approach this question by first identifying each substance listed. KOH is a strong base, so it's definitely not the strongest acid. H2O is water, doesn't seem like a strong acid. NH3 is ammonia, it's a weak base. That leaves us with HClO4 and HC2H3O2. Perchloric acid is a strong acid, HC2H3O2 is vinegar, a weak acid. By eliminating the bases and water, you turn this from a 20% chance of random guessing, to a 50:50 chance.
Check Table 4.2 in the text, the acids and bases listed in black are all "strong", those listed in pink are weak. For our purposes, any acid or base that is not listed in that table as being "strong" should be considered weak.
Other questions, let me know...
Which of the following is the strongest acid?
a.KOH (aq)
b.HClO4 (aq)
c.HC2H3O2 (aq)
d.H20 (aq)
e.NH3 (aq)
Strong acids (and bases) are those which ionize/dissolve completely when added to water. Let's approach this question by first identifying each substance listed. KOH is a strong base, so it's definitely not the strongest acid. H2O is water, doesn't seem like a strong acid. NH3 is ammonia, it's a weak base. That leaves us with HClO4 and HC2H3O2. Perchloric acid is a strong acid, HC2H3O2 is vinegar, a weak acid. By eliminating the bases and water, you turn this from a 20% chance of random guessing, to a 50:50 chance.
Check Table 4.2 in the text, the acids and bases listed in black are all "strong", those listed in pink are weak. For our purposes, any acid or base that is not listed in that table as being "strong" should be considered weak.
Other questions, let me know...
Review day....
Today we worked through a few review problems for the exam on Wednesday and talked about the density of gases for a minute or two.
SI sessions: Because of the exam, there will not be an SI session this Wednesday or Thursday. SI will resume next week.
Exam issues: If you choose to use a calculator, remember that graphing/programmable calculators are not allowed.
Feel free to email me any questions, I will posts answers to the blog. Good luck in your preparation.
SI sessions: Because of the exam, there will not be an SI session this Wednesday or Thursday. SI will resume next week.
Exam issues: If you choose to use a calculator, remember that graphing/programmable calculators are not allowed.
Feel free to email me any questions, I will posts answers to the blog. Good luck in your preparation.
2008-10-03
Gas stoichiometry and mixtures
We worked through a couple stoichiometry problems, including one that required use of the ideal gas law to determine the volume of gas produced by a reaction. These are the same stoichiometry problems that we've been working on for the last couple weeks, they just use different bits and pieces of info to get into and out of moles. We also talked about pressure and how the atomic understanding of "pressure" helps us understand mixtures of gases including Dalton's Law of Partial Pressures.
There is a new Mastering Chemistry assignment, due Tuesday. Exam #2 is next Wednesday. Have a good weekend.
There is a new Mastering Chemistry assignment, due Tuesday. Exam #2 is next Wednesday. Have a good weekend.
2008-10-01
Kinetic Molecular Theory and "Ideal" gases
Today we explored an explanation of the gas laws we talked about on Monday, the Kinetic Molecular Theory of Gases. Gas laws are based upon observation and tell us what happened or will happen; kinetic molecular theory attempts to explain why those observations happen. We had a new problem set in class today as well, it's posted on my web page.
I did not put up a new Mastering Chemistry assignment today, but there will almost certainly be a new one of Friday. Your next exam is next Wednesday, be sure to keep up on those MC assignments and take a look at the old exams on my web page.
I did not put up a new Mastering Chemistry assignment today, but there will almost certainly be a new one of Friday. Your next exam is next Wednesday, be sure to keep up on those MC assignments and take a look at the old exams on my web page.
2008-09-29
Redox and gas laws
Today we continued looking at redox reaction and oxidation numbers, and we talked about hints to classify rxn types. We moved into Chapter 5 and looked at the "simple" gas laws (Avogadro's, Boyle's, Charles') and the Ideal Gas Law in both linear and comparative forms. On Wednesday we will continue working with gas laws and other things related to gases.
There is a new Mastering Chemistry assignment posted. When I checked this morning, I believe only 10-12 people had even attempted the MC assignment that is due tonight. If you leave these assignments until the last minute, it's very difficult for me to help if problems pop up.
There is a new Mastering Chemistry assignment posted. When I checked this morning, I believe only 10-12 people had even attempted the MC assignment that is due tonight. If you leave these assignments until the last minute, it's very difficult for me to help if problems pop up.
2008-09-26
Solutions, stoichiometry and reaction types
Today we went through a solutions/stoichiometry problem and talked about gas-forming and redox reactions. We will spend a few more minutes on redox reactions on Monday before moving on to Chapter 5.
There's a new MC assignment posted. That means that right now there are 3 active MC assignments, one due tonight, one due Monday, and one due Tuesday. I'll remind you all once again, don't wait until the last minute to look at Mastering Chemistry assignments. Also, as we did in class today, I am happy to work through extra examples similar to the MC problems you might be struggling with, just let me know. The easiest way to do this is to send me an email, but you can also print off the problem you're stuck on and show me in class.
Have a good weekend.
There's a new MC assignment posted. That means that right now there are 3 active MC assignments, one due tonight, one due Monday, and one due Tuesday. I'll remind you all once again, don't wait until the last minute to look at Mastering Chemistry assignments. Also, as we did in class today, I am happy to work through extra examples similar to the MC problems you might be struggling with, just let me know. The easiest way to do this is to send me an email, but you can also print off the problem you're stuck on and show me in class.
Have a good weekend.
2008-09-24
Acid-Base reactions
Today we continued talking about types of reactions and why reactions happened. We started talking about "molecule-forming reactions", starting with acid-base reactions.
There's a new MC assignment posted, don't leave these until the last minute. The last time I check there were only 10-15 people who had started the MC assignment that's due on Friday.
There's a new MC assignment posted, don't leave these until the last minute. The last time I check there were only 10-15 people who had started the MC assignment that's due on Friday.
2008-09-22
Chem 150 Calendar
I've set up a Google Calendar for class, it's in the list of "Useful links" to the left. I'll do my best to keep it up to date with MC assignments, etc. If you have anything you feel should be included on the Chem 150 calendar, please let me know. I've already put the SI sessions on, although some of those may be moved/cancelled around exam times.
Solutions and precipitation reactions
We touched on a few topics today:
1. Reviewed solutions and molarity
2. Dilution calculations, if you can remember how to use C1V1=C2V2, you will rock dilutions
3. We began to discuss why reactions occur. The first reaction type we looked at is precipitation metathesis reactions. If two (or more) aqueous solutions of ionic solutes are combined and a precipitate can form, the reaction will occur to generate that precipitate. We need to look at solubility rules to predict whether or not a combination will form a precipitate. Solubility rules are summarized in your textbook, Table 4.1 on page 154.
4. We talked about the importance of net ionic reactions in understanding the chemistry that occurs in a reaction. Net ionic equations describe chemistry. One more time, if you just want to explore the chemistry of a reaction, the net ionic equation will give you the best picture. Full molecular/formula equations are important to understand what's being combined (macroscale), but net ionic equations describe the chemistry. For example, if I want to make some silver(I) carbonate solid, I can go into the stockroom and grab a bottle of silver(I) nitrate and a bottle of potassium carbonate, dissolve some of each in water, and combine the solutions to make a silver(I) carbonate precipitate as described by the following equation:
2 AgNO3(aq) + K2CO3(aq) --> Ag2CO3(s) + 2 KNO3(aq)
If I really want to describe the chemistry of this reaction, the potassium and nitrate ions aren't really doing anything. The only reason they're there is because I need to balance the charge of the silver(I) and carbonate ions in the solid reagents I get from the shelf. To describe the chemistry, I can (and probably should) use the net ionic equation:
2 Ag+(aq) + CO32-(aq) --> Ag2CO3(s)
Don't forget the old MC assignment (due tonight) and the new MC assignment (due Friday).
1. Reviewed solutions and molarity
2. Dilution calculations, if you can remember how to use C1V1=C2V2, you will rock dilutions
3. We began to discuss why reactions occur. The first reaction type we looked at is precipitation metathesis reactions. If two (or more) aqueous solutions of ionic solutes are combined and a precipitate can form, the reaction will occur to generate that precipitate. We need to look at solubility rules to predict whether or not a combination will form a precipitate. Solubility rules are summarized in your textbook, Table 4.1 on page 154.
4. We talked about the importance of net ionic reactions in understanding the chemistry that occurs in a reaction. Net ionic equations describe chemistry. One more time, if you just want to explore the chemistry of a reaction, the net ionic equation will give you the best picture. Full molecular/formula equations are important to understand what's being combined (macroscale), but net ionic equations describe the chemistry. For example, if I want to make some silver(I) carbonate solid, I can go into the stockroom and grab a bottle of silver(I) nitrate and a bottle of potassium carbonate, dissolve some of each in water, and combine the solutions to make a silver(I) carbonate precipitate as described by the following equation:
2 AgNO3(aq) + K2CO3(aq) --> Ag2CO3(s) + 2 KNO3(aq)
If I really want to describe the chemistry of this reaction, the potassium and nitrate ions aren't really doing anything. The only reason they're there is because I need to balance the charge of the silver(I) and carbonate ions in the solid reagents I get from the shelf. To describe the chemistry, I can (and probably should) use the net ionic equation:
2 Ag+(aq) + CO32-(aq) --> Ag2CO3(s)
Don't forget the old MC assignment (due tonight) and the new MC assignment (due Friday).
2008-09-19
Stoichiometry Friday
I'm posting this before class today because I am leaving town immediately following class. We will continue talking about stoichiometry, including limiting reagents and theoretical yields. I know this is going to sound familiar, but stoichiometry is all about practice, so start working on these things early and often.
There is a new MC assignment posted, due Monday.
Although Chem 150L is a separate course, I'll also take this opportunity to post a couple notes/reminders about lab.
1. Next week is the safety exam, be sure to review your notes and the PowerPoints of the safety lectures.
2. A few people still didn't have proper notebooks or goggles, make sure you have all of the required materials for lab. Also, writing in a lab notebook in pencil is not appropriate, regardless of the type of notebook you are using. Lab notebooks (for any class, not just chemistry) are intended to be a record of your activities in lab and are used to document any discoveries you make. These records should be kept in a manner more permanent than pencil.
3. With the nice weather this week, a number of people were wearing inappropriate footwear this week. You should only wear closed-toed shoes/boots to lab, no sandals, flip-flops, etc.
If you're looking for things to do (besides practicing stoichiometry problems) this weekend, there are a couple things I'm aware of:
1. The MSUM Volleyball team is at home Friday (7pm, vs. Bemidji) and Saturday (4pm, vs. UM-Duluth) at Nemzek.
2. The MSUM Soccer team is at home Saturday (11am, vs. Winona) and Sunday (1pm, vs. Upper Iowa), the soccer field is across the street north of the football field.
3. West Fest is happening this weekend in West Fargo, it's a community fair type event with a parade, car show, and other activities. For more info:
http://www.westfargochamber.com/Events/WestFest/tabid/66/Default.aspx
If anyone has other events or activities, post a comment. Have a good weekend.
There is a new MC assignment posted, due Monday.
Although Chem 150L is a separate course, I'll also take this opportunity to post a couple notes/reminders about lab.
1. Next week is the safety exam, be sure to review your notes and the PowerPoints of the safety lectures.
2. A few people still didn't have proper notebooks or goggles, make sure you have all of the required materials for lab. Also, writing in a lab notebook in pencil is not appropriate, regardless of the type of notebook you are using. Lab notebooks (for any class, not just chemistry) are intended to be a record of your activities in lab and are used to document any discoveries you make. These records should be kept in a manner more permanent than pencil.
3. With the nice weather this week, a number of people were wearing inappropriate footwear this week. You should only wear closed-toed shoes/boots to lab, no sandals, flip-flops, etc.
If you're looking for things to do (besides practicing stoichiometry problems) this weekend, there are a couple things I'm aware of:
1. The MSUM Volleyball team is at home Friday (7pm, vs. Bemidji) and Saturday (4pm, vs. UM-Duluth) at Nemzek.
2. The MSUM Soccer team is at home Saturday (11am, vs. Winona) and Sunday (1pm, vs. Upper Iowa), the soccer field is across the street north of the football field.
3. West Fest is happening this weekend in West Fargo, it's a community fair type event with a parade, car show, and other activities. For more info:
http://www.westfargochamber.com/Events/WestFest/tabid/66/Default.aspx
If anyone has other events or activities, post a comment. Have a good weekend.
2008-09-17
Test returned and started stoichiometry
Exams were returned in class today. If you did not take the exam but intend to continue in class please let me know, I will be forwarding names of those who are not continuing in class to the registrar next week. If you were not in class today to pick up your exam, I will have your exam with me on Friday in class. The average on the exam was 110/150.
We began talking about Chapter 4. Stoichiometry is all about balancing chemical equations, converting grams to moles and moles to grams. If you're struggling with balancing chemical formulas or these gram-mole/mole-gram conversions, you need to practice, practice, practice. We'll continue on Friday.
We began talking about Chapter 4. Stoichiometry is all about balancing chemical equations, converting grams to moles and moles to grams. If you're struggling with balancing chemical formulas or these gram-mole/mole-gram conversions, you need to practice, practice, practice. We'll continue on Friday.
2008-09-12
SI times and locations
I just noticed that Sara posted SI times and locations in a comment below, I'll repeat them:
Tuesday, LO 84, 1:30
Wednesday, BR 269, 5:30
Thursday, BR 268, 12:30
I hope that many of you are taking advantage of SI, regardless of your level of previous chemistry experience, it will help.
Tuesday, LO 84, 1:30
Wednesday, BR 269, 5:30
Thursday, BR 268, 12:30
I hope that many of you are taking advantage of SI, regardless of your level of previous chemistry experience, it will help.
Review day...
Today I answered questions in preparation for the exam on Monday. Be sure to look at the old exams on my web page to get an idea of the exam format and length. The front page of the exam has a periodic table and a number of physcial constants, take a look at what's available. If you have any questions, let me know, I will answer questions to this blog over the weekend.
A few policy/procedure notes/reminders for the exam on Monday:
1. No programmable calculators.
2. No cell phone calculators.
3. There must be at least 1 empty seat between you and your neighbor.
4. Turn off your cell phone. If your phone rings during the exam, you fail the course.
5. You are responsible for the polyatomic ions listed in Table 3.5, p.95 of the Tro textbook.
6. I do not expect you to memorize the whole periodic table, but I expect you to be able to use it. If you look at old exams, you will see that when I refer to an element I will often note the atomic number. This is to make it easier for you to find the element on the periodic table. For example, I don't expect you to know that rutherfordium has the symbol "Rf", but if I tell you that the atomic number of rutherfordium is 104, you should be able to find it very quickly on the periodic table and then be able to use the symbol, atomic mass, etc.
Good luck with your studying, let me know if there are questions.
A few policy/procedure notes/reminders for the exam on Monday:
1. No programmable calculators.
2. No cell phone calculators.
3. There must be at least 1 empty seat between you and your neighbor.
4. Turn off your cell phone. If your phone rings during the exam, you fail the course.
5. You are responsible for the polyatomic ions listed in Table 3.5, p.95 of the Tro textbook.
6. I do not expect you to memorize the whole periodic table, but I expect you to be able to use it. If you look at old exams, you will see that when I refer to an element I will often note the atomic number. This is to make it easier for you to find the element on the periodic table. For example, I don't expect you to know that rutherfordium has the symbol "Rf", but if I tell you that the atomic number of rutherfordium is 104, you should be able to find it very quickly on the periodic table and then be able to use the symbol, atomic mass, etc.
Good luck with your studying, let me know if there are questions.
2008-09-10
Organic compounds and balancing equations
Today in class we started talking about balancing chemical equations and we had a brief introduction to organic compounds. I'm not so concerned that you memorize all of the organic compounds we talked about today, but I wanted to go over some of the naming so that it's familiar when we use these substances in future examples.
In class on Friday we will be reviewing for the exam as long as necessary. If you have questions or topics for review, try to let me know ahead of time so I can prepare, or just come to class with questions. We will "review" as long as there is material to review, if we run out of review topics and problems we will start Chapter 4.
Sara will be leading an extra SI session to review for the exam at 11:30 on Friday.
In class on Friday we will be reviewing for the exam as long as necessary. If you have questions or topics for review, try to let me know ahead of time so I can prepare, or just come to class with questions. We will "review" as long as there is material to review, if we run out of review topics and problems we will start Chapter 4.
Sara will be leading an extra SI session to review for the exam at 11:30 on Friday.
2008-09-08
Mass % composition and formulas from %'s
Today we looked at percent composition and a couple ways to use percent composition to determine empirical and molecular formulas. In one of the problems I worked through on the board, I made a slight mistake, so I'll try to clear that up here. We worked through a problem where we came up with an empirical formula of CH_2_. The molar mass of this substance was stated to be 84 g/mol. So the question here is, what is the molecular formula of this substance? The mass of the empirical formula is 14 g/mol (OK, 14.027 g/mol, but that's close enough to 14 g/mol that we can round...). Since the molecular formula must be a multiple of the empirical formula, then we know that 14*(some whole number)=84. Solving, 84/14 = 6, so the molecular formula must be 6x the empirical formula, or C_6_H_12_.
Check out the Natural Sciences Research Night this evening at 5:30 in SL104. A number of faculty in the natural sciences will present brief descriptions of their research, so if you're interested in doing research this is a great opportunity to learn about what's going on.
Check out the Natural Sciences Research Night this evening at 5:30 in SL104. A number of faculty in the natural sciences will present brief descriptions of their research, so if you're interested in doing research this is a great opportunity to learn about what's going on.
2008-09-05
Moles, compound formulas, etc.
Today in class we talked about different types of compounds (ionic, molecular/covalent) and how to write electronically-balanced formulas for ionic compounds and balanced formulas for molecular/covalent compounds. Read/review the sections in your textbook on nomenclature. You will be responsible for all of the polyatomic ions listed in Table 3.5, page 95 of your text.
We also worked on a problem set in class. I've posted the problem set (as well as an answer key) on my web site (www.mnstate.edu/bodwin) on the Chem 150 page. Some of the questions on the problems set were intended to be challenging, so if you struggled with some of the questions that's a good thing, it will help you (and me) figure out where we all need to work a little more.
There are 2 new MC assignments posted, I was going to post one today and the other on Monday, but we've already touched on all the topics so I put them both up to give you more time to work on them. Do not wait until the last minute to do these assignments! We have already talked about everything except the last 2 questions in the second assignment, so you should be able to get a good start on these as soon as you have time to use a computer.
Have a good weekend and let me know if there are any problems/questions.
We also worked on a problem set in class. I've posted the problem set (as well as an answer key) on my web site (www.mnstate.edu/bodwin) on the Chem 150 page. Some of the questions on the problems set were intended to be challenging, so if you struggled with some of the questions that's a good thing, it will help you (and me) figure out where we all need to work a little more.
There are 2 new MC assignments posted, I was going to post one today and the other on Monday, but we've already touched on all the topics so I put them both up to give you more time to work on them. Do not wait until the last minute to do these assignments! We have already talked about everything except the last 2 questions in the second assignment, so you should be able to get a good start on these as soon as you have time to use a computer.
Have a good weekend and let me know if there are any problems/questions.
2008-09-03
Wednesday.....
Today in class we discussed the development of the Periodic Table, calculated the isotopic abundance of a mixture of nitrogen-14 and nitrogen-15, and developed the concept of the mole as a counting unit. If you're following along in the textbook, we've pretty much finished Chapter 2. Now, you're probably saying to yourself, "Hey, it's the 4th day of class and we've already burned through 2 chapters?!?!?!?!?!?" Yes, the first two chapters fly by VERY quickly, this is largely because Chapters 1 & 2 are a bit of a potpourri of little bits and pieces. If you've taken chemistry courses before, this should be review. If you've never had a chemistry class, this may seem to be a bit much. Regardless of your background, it's all about practice, practice, practice. We will be slowing down a bit as we move into Chapter 3 and beyond.
A few people have asked me about getting some help with the math involved in this course. This summer, I was made aware of a website that claims to address this very topic:
www.ChemReview.Net
I've looked over some of these tutorials, and they look like they should be helpful, so you might want to check it out. This website is a little more chemistry-specific, I'll do a little more digging to try and find a more general algebra tutorial. You can also come to me any time for help, either in person or via email.
Another resource is SI. Unfortunately, I forgot to jot down the location of tonight's SI session, so if someone could post that as a comment to this post it would be appreciated.
Also, tonight is the first Chem Club meeting of the year, 7pm in SL104. Come to the meeting to find out about what Chem Club is doing this year, what Chem Club can do for you, and what you can do for Chem Club. I've heard that there will be at least 1 interesting chemical demonstration at the meeting tonight.
Hmm, sounds like a good chemistry-related night. SI at 5:30, Chem Club meeting at 7.
A few people have asked me about getting some help with the math involved in this course. This summer, I was made aware of a website that claims to address this very topic:
www.ChemReview.Net
I've looked over some of these tutorials, and they look like they should be helpful, so you might want to check it out. This website is a little more chemistry-specific, I'll do a little more digging to try and find a more general algebra tutorial. You can also come to me any time for help, either in person or via email.
Another resource is SI. Unfortunately, I forgot to jot down the location of tonight's SI session, so if someone could post that as a comment to this post it would be appreciated.
Also, tonight is the first Chem Club meeting of the year, 7pm in SL104. Come to the meeting to find out about what Chem Club is doing this year, what Chem Club can do for you, and what you can do for Chem Club. I've heard that there will be at least 1 interesting chemical demonstration at the meeting tonight.
Hmm, sounds like a good chemistry-related night. SI at 5:30, Chem Club meeting at 7.
2008-08-29
Friday's class and SI info
Today we talked about the various Laws, Hypotheses and Theories that have given us our current understanding of the atom.
SI information:
Your SI Leader is Sara Collier.
SI sessions: Tuesdays 1:30-2:20, Wednesday 5:30-6:20, Thursday 12:30-1:20
Office hour: Tuesdays 12:30-1:20 in BR260.
I'll post the SI locations as soon as they are scheduled. I encourage everyone to check out SI, it is a very helpful program and will help you succeed.
There is also a new MC assignment posted. A note on MC, your assignments are always due by 11:59pm on the due date, but do not wait until the last minute to attempt the assignments.
Chem 150L lab sections will begin meeting next week, so I will see a number of you at 9am Tuesday morning. Have a good weekend.
SI information:
Your SI Leader is Sara Collier.
SI sessions: Tuesdays 1:30-2:20, Wednesday 5:30-6:20, Thursday 12:30-1:20
Office hour: Tuesdays 12:30-1:20 in BR260.
I'll post the SI locations as soon as they are scheduled. I encourage everyone to check out SI, it is a very helpful program and will help you succeed.
There is also a new MC assignment posted. A note on MC, your assignments are always due by 11:59pm on the due date, but do not wait until the last minute to attempt the assignments.
Chem 150L lab sections will begin meeting next week, so I will see a number of you at 9am Tuesday morning. Have a good weekend.
2008-08-27
Wednesday
Today in class we defined chemistry (the study of matter and its changes), discussed the scientific method, classification of matter, physical and chemical changes, and worked through a conversion problem to demonstrate our procedure for solving problems (sort, strategize, solve, check).
Lab manuals ($5) and goggles ($5) will be on sale outside SL104 before (and after?) class on Friday. They are also available in the Chemistry Department Office (HA407). Cash or checks are accepted.
The course ID# for Mastering Chemistry is: C150F08JB2
Our SI leader will be introducing herself and letting you know a little about SI and her schedule on Friday. I'll post the info on Friday after class.
Lab manuals ($5) and goggles ($5) will be on sale outside SL104 before (and after?) class on Friday. They are also available in the Chemistry Department Office (HA407). Cash or checks are accepted.
The course ID# for Mastering Chemistry is: C150F08JB2
Our SI leader will be introducing herself and letting you know a little about SI and her schedule on Friday. I'll post the info on Friday after class.
2008-08-25
First day, getting started
Just a few notes on getting things started:
1. Chemistry 150L will not be meeting this week. Lab manuals and goggles will be available for sale before and after class on Wednesday outside SL104 by members of the Chem Club, I'll double check on the price. Chem Club accepts cash or checks.
2. Sign up/register for Mastering Chemistry as soon as possible and work through the assignment "Introduction to Mastering Chemistry" first. The second assignment, "Working with Numbers 1", is a live assignment, you will be earning (or losing) points on that assignment.
3. If you have not registered for a Chemistry 150L section, and you intend to register for Chemistry 150L, please do so as soon as possible, spots are filling up.
That's it for now, see you Wednesday.
1. Chemistry 150L will not be meeting this week. Lab manuals and goggles will be available for sale before and after class on Wednesday outside SL104 by members of the Chem Club, I'll double check on the price. Chem Club accepts cash or checks.
2. Sign up/register for Mastering Chemistry as soon as possible and work through the assignment "Introduction to Mastering Chemistry" first. The second assignment, "Working with Numbers 1", is a live assignment, you will be earning (or losing) points on that assignment.
3. If you have not registered for a Chemistry 150L section, and you intend to register for Chemistry 150L, please do so as soon as possible, spots are filling up.
That's it for now, see you Wednesday.
2008-08-18
Welcome to Chem 150
Welcome to Dr. Bodwin's General Chemistry Blog. This blog is intended to be a 1-stop resource for students enrolled in my General Chemistry classes. After class each day, I will post a brief summary of the day's class as well as any class announcements or other information. This blog is not a source of "lecture notes", if you want notes on a day's class then you should attend class or find a friend who is willing to share his/her notes with you.
This blog will also be open for comments, so if you have a question on the material we are working with, post it. You are also welcome to email me questions directly, but I will respond to all content-related questions on the blog.
I hope this is a useful resource, and I welcome any suggestions for improvement. Let's have a great semester!
This blog will also be open for comments, so if you have a question on the material we are working with, post it. You are also welcome to email me questions directly, but I will respond to all content-related questions on the blog.
I hope this is a useful resource, and I welcome any suggestions for improvement. Let's have a great semester!
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