Chemistry 2710 Review Problems: Hints and Answers

1. 2. The can be used to calculate the concentration of a product. The initial rate is .
2. 1. With this much data, it's best to use a graphical method. It simplifies certain calculations is you convert the to . The order of the reaction is 1. The rate constant is .
   2. Not elementary. Hint: It has something to do with the rate law.
3. 1. with
5. 
7. 
8. Because the initial concentrations are equal and the stoichiometry is 1:1, the two concentrations will always be equal, making this an instance of a simple rate law. The concentration after 10min is 0.038mol/L.
9. 
11. 1. 
    3. . Your answer may look a little different from mine, but you should get the same results in the next part if you did this right.
    4. The following table shows the half-life computed for a few different initial conditions:

       

12. You have to do a little stoichiometry to determine the pressure of A: where is the initial pressure of A (400mmHg). You need another equation which related and to P. The reaction is of the second order. Since I didn't tell you what units I want the rate constant in, you might as well use the pressure units I gave you and save yourself a little trouble: .
13. This has something to do with plotting a line.
14. The 47 decays per day is 47 atoms that undergo reaction per day. Since this is a first-order process, where k is the rate constant and N is the number of atoms of in the sample. The half-life is .
15. 1. Plot ln P vs t, the slope is the specific growth rate of the population (k). The doubling time computed from k is 77y.
    2. Prediction is tricky. My fit of the data is

       

       We are looking for the t at which . I get about 2005. However, if you plot all the data, you will see that the graph of vs t has considerable curvature. The population growth is in fact slowing down. If I refit only the data from the last two decades (which should give a much more accurate estimate of the current rate of growth), I predict that the Finnish population will reach 6 million in 2031.

    3. See above.