Exam 1B, Spring 2005

1. Nomenclature:

a. Give the name for Cr₂O₇^2–

b. Give the molecular formula for the dihydrogen phosphate ion.

2. Briefly (15 words or less) distinguish between an activated complex and an intermediate.

3. For the reaction shown below:

CO(g) + NO(g) → CO₂(g) + N₂(g)

a. What is the ratio of the rate of loss of nitrogen oxide compared to the rate of gain of nitrogen?

b. Is this an elementary reaction? Why or why not?

4. Consider the following reaction:

H₂O₂(aq) → H₂O(l) + O₂(g)

which has a rate law of Rate = –k, where k = 1.0×10^–3 M s^–1. If [H₂O₂]_initial = 1.0 M and [O₂]_initial = 0.0 M, answer the following questions:

a. What is the order of reaction with respect to hydrogen peroxide?

b. What is the concentration of hydrogen peroxide at t = 100 s?

c. What is the concentration of oxygen at t = 100 s?

5. The data listed below was collected for the following reaction:

2 HgCl₂(aq) + C₂O₄^2–(aq) → 2 Cl^–(aq) + 2 CO₂(g) + Hg₂Cl₂(s)

Experiment [HgCl₂] (M) [C₂O₄^2–] (M) Initial Rate (M min^–1)

1 0.10 0.20 4.0×10^–5

2 0.10 0.40 1.6×10^–4

3 0.050 0.40 8.0×10^–5

4 0.050 0.20 2.0×10^–5

a. What is the rate law for the reaction?

b. What is the value of the rate constant for the reaction?

6. The following mechanism was proposed for a reaction:

OCl^–(aq) + H₂O(l)→ ← HOCl(aq) + OH^–(aq)

I^–(aq) + HOCl(aq) → HOI(aq) + Cl^–(aq)

HOI(aq) + OH^–(aq) → H₂O(l) + OI^–(aq)

a. Write the net reaction.

b. What is the molecularity of each reaction in the mechanism?

c.Which step is not rate determining? Why?

7. Write the mass action expression for K_c for the following reactions.

a. CO₂(g) + H₂(g) → ← CO(g) + H₂O(g)

b. NO(g) + H₂O(g) → ← O₂(g) + NH₃(g)

c. NH₄HS(s) → ← H₂S(g) + NH₃(g)

8. For the reaction:

N₂(g) + O₂(g) → ← 2 NO(g)

K_c = 4×10^–4.

Find K_c for the reaction:

NO(g) → ← ½ N₂(g) + ½ O₂(g)

Answers