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AP Chemistry Review: Unit 7

Total questions: 15

Worksheet time: 15mins

Name
Class
Date
1.

At equilibrium, concentrations of reactants and products are

a)

equal

b)

constant

2.

At what time does the system first reach equilibrium?

a)

24s

b)

40s

c)

60s

d)

80s

3.

H2 gas and N2 gas were placed in a rigid vessel and allowed to reach equilibrium in the presence of a catalyst according to the following equation.

3 H2(g) + N2(g) ⇄ 2 NH3(g)         ΔHo = -92 kJ/molrxn

The diagram below shows how the concentrations of H2 , N2 , and NH3 in this system changed over time. What occurs from t1 to t2?

a)

The concentration of N2 decreased.

b)

The number of effective collisions between H2 and N2 was zero.

c)

The rates of the forward and reverse reactions were equal.

d)

The rate of formation of NH3 molecules was equal to the rate of disappearance of H2 molecules.

4.

H2(g)+I2(g)⇄2HI(g)

Hydrogen gas reacts with iodine gas at constant temperature in a sealed rigid container. The gases are allowed to reach equilibrium according to the equation above. Which of the following best describes what will happen to the reaction immediately after additional iodine gas is added to the system?

a)

The rates of both the forward and reverse reactions decrease.

b)

The rates of both the forward and reverse reactions do not change.

c)

The rate of the forward reaction becomes greater than the rate of the reverse reaction.

d)

The rate of the forward reaction becomes less than the rate of the reverse reaction.

5.

H2(g) + I2(g) ⇄ 2HI(g)

A 1.0mol sample of H2(g) and a 1.0mol sample of I2(g) are placed in a previously evacuated 1.0L container and allowed to reach the equilibrium shown above. If the equilibrium concentration of HI(g) is 0.40M, which of the following is the value of the equilibrium constant?

a)

0.16

b)

0.25

c)

0.44

d)

1.0

6.

Given the Kc for a forward reaction, how can you find Kc for the reverse reaction?

a)

Divide Kc by 1

b)

Divide 1 by Kc

c)

Square Kc

d)

Take the square root of Kc

7.

For the reaction...

SO2 + O2 <−> SO3

If the concentration of SO2 is increased, the system will shift ___________.

a)

left

b)

right

c)

left and right

d)

neither left nor right

8.

For the reaction...

heat + N2 + O2 ↔ 2NO

If heat is added to the chemical system, the system will shift _______.

a)

left

b)

right

c)

left and right

d)

neither left nor right

9.

2SO2 (g) + O2 (g) ⇌ 2SO3 (g)

Decreasing the volume of container will

a)

shift the system right

b)

shift the system left

c)

change K

d)

have no effect

10.
An equilibrium constant with a large value, e.g. Kc = 1000, indicates…
a)
A very fast reaction
b)
Mostly products at equilibrium
c)
Mostly reactants at equilibrium
d)
Nothing useful at all
11.
If K < Q, which part of the reaction will speed up?
a)
forward
b)
reverse
c)
none
12.
The molar solubility of PbI2 is 1.52 x 10-3 M. Calculate the value of Ksp for PbI2.
a)
3.51 x 10-9
b)
1.40 x 10-8
c)
4.62 x 10-6
d)
1.52 x 10-3
13.
The correct mathematical expression for finding the molar solubility (s) of Sn(OH)2 is:
a)
2s2 = Ksp
b)
2s3 = Ksp
c)
4s3 = Ksp
d)
8s3 = Ksp
14.

Which of the following must be true for a reaction that proceeds spontaneously from initial standard state conditions?

a)

ΔG° > 0 and Keq > 1

b)

ΔG° > 0 and Keq < 1

c)

ΔG° < 0 and Keq > 1

d)

ΔG° < 0 and Keq < 1

15.

When a reaction at equilibrium is reversed,

a)

the K value's sign is flipped

b)

the K value is divided by 2

c)

the K value is the reciprocal of original k