Reaching equilibrium...

When you study the kinetics of a reaction for a long enough time, the reaction reaches equilibrium. We've hit the high points of kinetics (rates, rate laws, integrated rate laws, activation energies, mechanism) and now we have reached equilibrium. Equilibrium is the state where the forward and reverse rates of reaction are equal, so although those reactions both continue to occur, the concentration of reactants and products remains constant.

Looking at the schedule, our next exam is coming up Wednesday Feb. 24th. Because of my schedule, it is extremely unlikely that I will ever be able to grade a Wednesday exam by class time on Friday, and given that kinetics and equilibrium are both pretty large topics, I think it would be best to move that exam back to Friday Feb. 26th. If anyone has a significant conflict with that day (other exams, plans to be out of town, etc.), let me know. At this point, the exam will still be scheduled for Wednesday Feb 24th, but if I don't hear of too many conflicts we will probably move it to Friday Feb 26th.

Arrhenius says...

We looked at a few examples of rate law problems and have determined rate law orders by comparing experiments with differing initial concentrations of reactants.

Kinetics is all about probability, and that probability is dependent upon the activation energy required to get a reaction started. Activation energy is calculated using the Arrhenius equation. We looked at the compact form of the Arrhenius equation (very elegant in its simplicity, but not always very practically useful) and derived a couple variations that are more useful, the comparative and linear forms.

As with so many things, kinetics problems become easier with practice, so keep up on your Mastering Chemistry and take a look at some textbook problems. The new MC assignment is posted.

Have a good weekend.

There oughta be a (rate) law!

We looked at average rates and instantaneous rates, almost did some calculus but not quite. The only unique instantaneous rate is the initial rate and we looked at Rate Laws as a relationship between the initial rate of a reaction and the concentrations of the reactants. Rate laws give us insight into the molecule-scale pathway of the reaction.

I handed back exams, if you didn't pick yours up I will have them with me in class on Wednesday and Friday.