exam4-chap10-kineticsandequilibrium.pdf

QUIZ – EQUILIBRIUM and KINETICS ANSWER SHEET Part I Brief Response Succinctly and completely answer each question. (3 pts each)

#1-2 The table below represents the production of 50 mL of CO2 in the reaction of HCl with NaHCO3. Five trials

were performed under different conditions as shown. The same mass of NaHCO3 was used in each trial.

Trial Particle Size of NaHCO3 Concentration of HCl Temperature of HCl

A small 1 M 20 ºC

B large 1 M 20 ºC

C large 1 M 40 ºC

D small 2 M 40 ºC

1. Which trial would produce the fastest reaction?

2. Which two trials could be used to measure the effect of surface area?

3. What is the name for the energy needed to start a chemical reaction?

4. A reaction is most likely to occur when reactant particles collide with

5. Joey put 100 mL of HCl (aq) into four bakers under the

conditions shown. If he adds a 2.0-cm strip of

magnesium ribbon, then which beaker will have the

fastest reaction? Why?

6. Which equilibrium constant indicates the highest concentration of product? Explain.

A) K = 1 × 10–1 B) K = 2 × 10–2 C) K = 3 × 10–3 D) K = 4 × 10–4

7. Given the reaction at equilibrium: H2(g) + Br2(g) ⇌ 2 HBr(g). What is the relationship between the rate of the forward reaction and the rate of the reverse reaction?

8. Which is the equilibrium expression for the reaction: 2CO(g) + O2(g) ⇌ 2 CO2(g)?

9. Which a chemical equation that would corresponds to the following equilibrium expression? 2

3

[A] [B]

[C] K =

10. Consider: 2H2(g) + O2 (g) ⇌ 2H2O(g) + heat, if the pressure increases due to a decrease in volume, then what is the effect on the concentration of oxygen, [O2? Explain.

11. Given: 2A(g) + 3 B (g) ⇌ A2B3(g) + heat, what change will not effect the concentrations of A, B or A2B3? Why?

A) adding more A B) adding a catalyst

C) increasing the temperature D) increasing the pressure

QUIZ – EQUILIBRIUM and KINETICS ANSWER SHEET 12. Given: N2(g) + O2(g) + energy ⇌ 2NO(g), which change results in a decrease in the amount of NO(g)? Why

A) decreasing the pressure

B) increasing the concentration of O2

C) decreasing the concentration of N2(g)

D) increasing the temperature

Part II Extended Response Solve each problem. Neatly display all work, units and significant figures. (45 pt.)

13. Which is the correct equilibrium expression for each reaction: (8 pts)

a. 2H2O(g) + 4KO2 (s) ⇌ 4KOH(s) + 3O2(g)?

b. CuO (s) + H2 (g) ⇌ Cu (l ) + H2O (g)

14. For the equilibrium system: 2HBr(g) ⇌ Br2(g) + H2(g) the equilibrium constant K, is 6.45 x 10-4. (4 pts)

Which side is favored: reactants (left) or products (right)? Explain.

15. N2(g) + 2O2 (g) ⇌ 2NO2(g) 16. 2NBr3 (g) ⇌ N2 (g) + 3Br2 (g) What is the equilibrium constant, K, if a 2.0 L flask Determine the concentration of nitrogen gas, N2, when

with 0.24 mol N2, 0.76 mol O2 and 4.4 mol NO2 is at a 3.0 L flask contains 0.36 mole of Br2, and

equilibrium? (6 pts) 0.086 mole of NBr3 at equilibrium. K is 0.0024. (6 pts)

17. For each change, state whether the concentration of oxygen gas, O2, will increase, decrease or remain unchanged. AND

WHY that change occurs for the equilibrium system: 2H2(g) + O2 (g) ⇌ 2H2O(g) + heat. (9 pts)

a. Water is added.

b. Temperature is decreased.

c. Hydrogen, H2, is removed.

18. For each change in experimental conditions,

state whether the number of collisions would increase or decrease or remain unchanged, and

state whether the reaction rate would increase or decrease or remain unchanged. (10 pts)

Number of Collisions Reaction Rate

a. decrease concentration of a reactant

b. increase temperature for an endothermic reaction

c. increase the volume of a solution

d. decrease the volume of a gas phases reaction

e. a catalyst is added

19. For the reaction: Cl2O(g) + H2O(g) ⇌ 2HOCl(g), the equilibrium constant, K, is 0.0090.

What is the value of the equilibrium constant, for the reaction:

a. 2HOCl(g) ⇌ Cl2O(g) + H2O(g) ? (6 pts)

a. 2 Cl2O(g) + 2 H2O(g) ⇌ 4HOCl(g)? (6 pts)

20. Is the system, 2NBr3 (g) ⇌ N2 (g) + 3Br2 (g), at equilibrium when the concentration of nitrogen, N2, is 0.80M, (5 pts)

bromine, Br2, is 2.4 M, and nitrogen tribromide, NBr3, is 0.0010 M with an equilibrium constant K of 0.0024?

If the reaction is not at equilibrium which way will it shift to achieve equilibrium? Explain.