Iowa State University / Leaders: / Kyle and Shealyn
Course: / Chem 178
Instructors: / Burnett and Vela
Date: / 4-13-14
1. What are the four things that affect the rate of a chemical reaction?
2. Draw a graph of the concentrations of the products and the reactants versus time in a chemical reaction.
3. What is the difference between average rate and instantaneous rate?
The following data (use for questions 4-5) was collected for the rate of disappearance of HCl in the reaction:
CH3OH (aq) + HCl (aq) => CH3Cl (aq) + H2O (l)
Time (min) / [HCl] (M)0.0 / 1.85
54.0 / 1.58
107.0 / 1.36
215.0 / 1.02
430.0 / 0.58
4. Calculate the average rate between 0 and 54 minutes.
5. Calculate the average rate between 0 and 430 minutes. How does it compare to the answer in number 4
6. Write the integrated rate law for a zero order, first order, and second order reaction.
For the following reaction (use for questions 7-9): SO2 + O3 => SO3 + O2
Experiment / [SO2], M / [O3], M / Initial Rate, M/s1 / 0.25 / 0.40 / 0.118
2 / 0.25 / 0.20 / 0.118
3 / 0.75 / 0.20 / 1.062
7. What is the rate law expression?
8. What is the rate constant?
9. What are the units of the rate constant?
For the following reaction (use for questions 10-14): 2 NO2 2 NO + O2
Time (sec) / [NO2], M / ln[NO2] / 1/[NO2]0 / 0.100
5.0 / 0.017
10.0 / 0.0090
15.0 / 0.0062
20.0 / 0.0047
10. For a reaction that is first order, what must be plotted in order to get a linear graph? For a reaction that is second order, what must be plotted in order to get a linear graph?
11. Is this reaction first or second order?
12. What is the rate constant?
13. If you used the method of initial rates to obtain the order for NO2, predict what reaction rates you would measure in the beginning of the reaction for initial concentrations of 0.200 M, 0.100 M, and 0.050 M.
14. What is the rate at t=17 seconds if the initial concentration of NO2 is 0.3M?
15. What is the difference between the half-life of a first and second order reaction?
16. Calculate the fraction of atoms in a sample of argon gas at 450K that has an energy of 10.0 kJ or greater.
17. Draw a graph of potential energy vs reaction progress for a reaction with 2 intermediates.
18. What are the expected signs of ∆H and ΔS for the freezing of water?
The following mechanism is proposed:
H2 (g) + ICl (g) => HI (g) + HCl (g)
HI (g) + ICl (g) => I2 (g) + HCl (g)
19. Write the balanced equation for the overall reaction.
20. Identify all the intermediates in the reaction
21. If the first step is slow and the second step is fast, which rate law do you expect to be observed for the overall reaction?
Given the following information at 25˚C:
H2O (l) => H- (aq) + OH- (aq)
(Gf˚)298 (kJ/mol) -237.2 0 -157.3
(Hf˚)298(kJ/mol) -285.8 0 -230.0
22. Calculate the pH of water at 42 ˚C
23. The normal boiling point of ethanol, C2H5OH, is 78.3 ˚C. Its molar enthalpy of vaporization is 38.56 kJ/mol. What is the change in entropy in the system when 68.3 grams of ethanol at 1atm condenses to liquid?
NH4NO3(s) + H2O(l) NH4+(aq) + NO3-(aq)
Compound Hfo(kJ/mol) S(J/mol-K)
NH4NO3(s) -365.56 151.08
NH4+(aq) -132.51 113.4
NO3-(aq) -205.0 146.4
24. Calculate ∆H and ΔS for this reaction.
25. Is this reaction spontaneous at 20 ˚C?