Download Practice Test: Equilibrium

Name ______________________ Period _____
PreAP Chem Test Review: Equilibrium
Short Answer
Write equilibrium expressions for the following reactions. Be sure to balance the equations first!
1.
NH4HS(g)
2.
HCl(g) + O2(g)
3. C (s) + O2 (g)
NH3(g)+ H2S(g)
Cl2(g) + H2O(g)
CO2 (g)
4. HCl (aq) + H2O (l)  H3O+ (aq) + Cl- (aq)
At 793 K, for the reaction:
NCl3(g) + Cl2(g)
NCl5(g) + heat
Keq = 39.3.
5. Do products or reactants dominate in this equilibrium? ____________________
6. If the system is at equilibrium and 5.0 moles of chlorine are added, what will be the new Keq? ______
7. If the system is at equilibrium and the container is doubled in size, what will be the new Keq? ______
8. What will happen to Keq if the temperature is lowered? ____________
9. In summary, what is the only thing that will change the equilibrium constant? _____________________________
Which way would the equilibrium shift (right or left) if the following changes are made to the equilibrium:
10. H2(g) +Br2(g)
2HBr(g) + heat
Add Hydrogen gas _______
11. C(s) + CO2(g)
Increase the volume of the container _____
Lower the temperature _______
2CO(g)
Add carbon monoxide _____
Add Carbon _____
12. What is a reversible reaction?
13. Are most reactions reversible? ________
Decrease the volume of the container ______
Name ______________________ Period _____
14. For each reaction below, state whether increasing or decreasing the volume of the reaction vessel would yield more
product at equilibrium.
N2O4(g)
2NO2(g) ____________________
2SO3(g)
2SO2(g) + O2(g) _____________________
15. In which direction (left or right) would an increase in temperature shift the equilibrium?
Heat + H2(g) + I2(g)
CH4(g) + 2O2(g)
2HI(g) ______________
CO(g) + 2H2O + heat _______________
Problems
At 773 K, the reaction 2NO(g) + O2(g)
2NO2(g) produces the following concentrations at equilibrium:
[NO] = 3.49  10–4M; [O2] = 0.80M; [NO2] = 0.25M.
15. What is the equilibrium expression for the reaction?
16. What is the equilibrium constant for the reaction?
17. Phosphorous pentachloride decomposes to phosphorous trichloride according to this equation:
PCl5(g)
PCl3(g) + Cl2(g) Keq = 1.00  10–3.
At equilibrium, [PCl5] = 1.00M and [Cl2] = 3.16  10–2M. What is the equilibrium concentration of PCl3?
18. For the reaction:
2HBr (g)  H2 (g) + Br2 (g)
0.500M HBr decomposes until equilibrium is reached. At equilibrium, the concentration of bromine gas is found to be
0.130 M. Calculate Keq.
19. Consider the following equilibrium: Cl2(g) + 2NO(g) ⇌ 2NOCl(g)
At equilibrium, [Cl2] = 1.0 M and [NO] = 2.0 M.
What is the [NOCl] at equilibrium?
A.
0.80 M
B.
0.89 M
C.
4.5 M
D.
20 M
Keq = 5.0
Name ______________________ Period _____
+ 2NO(g) ⇌ 2NOCl(g)
Inititally, 12.0 moles of Cl2, 10.24 moles of NO, and 2.00 moles NOCl are placed in a
2.00 L container. If there are 10.0 moles NOCl at equilibrium, calculate the Keq.
A.
0.996
B.
5.58
C.
1.12
D.
4.98
20. Consider the following equilibrium: Cl2(g)
21. For the equilibrium: 2 NO (g)  N2 (g) + O2 (g)
If 1.45 moles each of N2 (g) and O2 (g) are introduced
in a container that has a volume of 6.00 liters, and allowed to reach equilibrium at 300 K, the equilibrium concentration of oxygen gas is 0.112. What is Keq at 300 K?
22. In which direction would the equilibrium shift if the temperature is increased?
(a)
(b)
23.
2H2O(g) ↔ 2H2(g) + O2(g)
ΔH = 484 kJ
C3H8(g) + 5O2(g) ↔ 3CO2(g) + 4H2O(g)
ΔH = -2043 kJ
_______________
_______________
Use this reaction to answer the next two questions: C2H6(g) + Cl2(g) ↔ C2H5Cl(s) + HCl(g)
What happens to the amount of C2H6 when HCl gas is added? _____________________
What happens to the amount of C2H6 when C2H5Cl is added? _____________________
24. Consider the following equilibrium:
A chemist places 2.00 mol NOCl in a 1.0 L container. Describe the changes in [NOCl] and [Cl2] as the
system approaches equilibrium.
25. What is “equal” in a chemical reaction that has reached a state of equilibrium?
___________________________________________________________________________________
26. Consider the following equilibrium system:
In an experiment, a student places the above equilibrium system into a cold water bath and notes that the intensity of the
red color increases. The student then concludes that the equilibrium is exothermic.
Do you agree or disagree? Explain.
Name ______________________ Period _____
27.
28. Which of the following describes all chemical equilibrium systems?
A. The mass of the reactants equals the mass of the products.
B. The chemicals are present in the same ratio as in the balanced equation.
C. The rate of the forward reaction equals the rate of the reverse reaction.
D. The concentration of the reactants equals the concentration of the products.
E. More than one of these.
29.
30.
31.
Name ______________________ Period _____
32.
33.
34.
35.
36.
Name ______________________ Period _____
37.
38.
39.
40.
41.
Name ______________________ Period _____
42.
43. Consider the following equilibrium system.
I2(g)
+
Cl2(g) ⇄ 2 ICl (g) + energy
Label the graph that best represents each of the following stresses and shift.

adding I2(g)

increasing the temperature

increasing the volume

removing Cl2(g)
I2
I2
ICl
ICl
I2
I2
ICl
Cl2
Name ______________________ Period _____