ch 15 - calculations

Question 1

At 25 °C, the decomposition of dinitrogen tetraoxide
N2O4(g) 2 NO2(g)
has an equilibrium constant (Kp) of 0.144. At equilibrium, the total pressure of the system is 0.0758 atm. What is the partial pressure of each gas?
0.0745 atm NO2(g) and 0.0385 N2O4(g)
0.0549 atm NO2(g) and 0.0209 N2O4(g)
0.0531 atm NO2(g) and 0.0227 N2O4(g)
0.0502 atm NO2(g) and 0.0256 N2O4(g)
0.0381 atm NO2(g) and 0.0377 N2O4(g)

Answer 1

not c.

Question 2

What is the reaction quotient, Q, for the equilibrium
CuCl(s) Cu+(aq) + Cl−(aq)

when 0.3746 L of M Cu+ is combined with 0.4326 L of M Cl− in the presence of an excess of CuCl(s)?

Answer 2

not b.

Question 3

For the reaction given below, 2.00 moles of A and 3.00 moles of B are placed in a 6.00-L container.
A(g) + 2B(g) C(g)

At equilibrium, the concentration of A is 0.230 mol/L. What is the value of Kc?

1.20
1.53
5.22
0.230
0.449

Answer 3

not b.

Question 4

Given the following chemical equilibrium COCl2(g) CO(g) + Cl2(g), calculate the value of Kc when Kp = 6.5 × 1011 at 298 K. (R = 0.08206 L⋅atm/mol ⋅ K)
1.5 × 10–12
3.8 × 10–11
1.1 × 109
2.7 × 1010
1.6 × 1013

Answer 4

not c. or b.

Question 5

Excess Ag2SO4(s) is placed in water at 25 °C. At equilibrium, the solution contains 0.029 M Ag+(aq). What is the equilibrium constant for the reaction below?
Ag2SO4(s) 2 Ag+(aq) + SO42–(aq)
1.8 × 10–7
6.1 × 10–6
1.2 × 10–5
2.4 × 10–5
8.4 × 10–4

Answer 5

not e.

Question 6

Given the following equilibria,
Ni2+(aq) + 2 OH–(aq) Ni(OH)2(s) K1 = 1.8 × 1015
Ni2+(aq) + 4 CN–(aq) Ni(CN)42–(aq) K2 = 2.0 × 1031
determine the equilibrium constant, Kc, for the following reaction.
Ni(OH)2(s) + 4 CN–(aq) Ni(CN)42–(aq) + 2 OH–(aq)

2.8 × 10–47
9.0 × 10–17
1.8 × 1015
1.1 × 1016
3.6 × 1046

Answer 6

not b.

Question 7

The equilibrium constant (Kc) for the decomposition of ammonium hydrogen sulfide, NH4HS(s) NH3(g) + H2S(g), is 1.8 × 10–4 at 25 °C. If excess NH4HS(s) is allowed to equilibrate at 25 °C, what is the equilibrium concentration of NH3?
3.2 × 10–8 M
9.0 × 10–5 M
1.8 × 10–4 M
6.7 × 10–3 M
1.3 × 10–2 M

Answer 7

not c.

Question 8

Consider the following equilibrium:
CO2(g) + H2(g) CO(g) + H2O(g); Kc = 1.6 at 1260 K

Suppose 0.019 mol CO2 and 0.030 mol H2 are placed in a 3.00-L vessel at 1260 K. What is the equilibrium partial pressure of CO(g)? (R = 0.0821 L · atm/K·mol)

4 atm
0.35 atm
1.6 atm
0.66 atm
1 atm

Answer 8

not e.

Question 9

Sulfuryl chloride decomposes to sulfur dioxide and chlorine.
SO2Cl2(g) SO2(g) + Cl2(g)
Kc is 0.045 at 648 K. If an initial concentration of 0.075 M SO2Cl2 is allowed to equilibrate, what is the equilibrium concentration of Cl2?
0.0034 M
0.030 M
0.040 M
0.058 M
0.075 M

Answer 9

not b.

Question 10

The equilibrium constant at 25 °C for the dissolution of silver iodide is 8.5 × 10–17.
AgI(s) Ag+(aq) + I–(aq)
If an excess quantity of AgI(s) is added to water and allowed to equilibrate, what is the equilibrium concentration of I–?
7.2 × 10–33 M
4.3 × 10–17 M
8.5 × 10–17 M
6.5 × 10–9 M
9.2 × 10–9 M

Answer 10

not d.

Question 11

Nitrogen and oxygen gases may react to form nitrogen monoxide. At 1500 °C, Kc equals 1.0 × 10−5.
N2(g) + O2(g) 2 NO(g)
If 0.030 mol N2 and 0.030 mol O2 are sealed in a 1.0 L flask at 1500 °C, what is the concentration of NO(g) when equilibrium is established?

3.0 × 10−7 M
4.7 × 10−5 M
9.5 × 10−5 M
3.0 × 10−2 M
9.1 × 101 M

Answer 11

not a.

Question 12

Nitrogen trifluoride decomposes at to form nitrogen and fluorine gases according to the following equation:
2NF3(g) N2(g) + 3F2(g)

2.50-L reaction vessel is initially charged with 1.22 mol of NF3 and allowed to come to equilibrium at 800 K. Once equilibrium is established, the reaction vessel is found to contain 0.0194 mol of N2. What is the value of Kp at this temperature? (R = 0.0821 L⋅atm/mol⋅K)

2.68 × 10–6
1.91 × 10–3
1.79 × 10–3
2.77 × 10–6
4.43 × 10–7

Answer 12

not c.

Question 13

A 3.50-mol sample of HI is placed in a 1.00-L vessel at 460°C, and the reaction system is allowed to come to equilibrium. The HI partially decomposes, forming 0.266 mol H2 and 0.266 mol I2 at equilibrium. What is the equilibrium constant Kc for the following reaction at 460°C?
½ H2(g) + ½ I2(g) HI(g)

1.23 × 102
8.10 × 10–3
2.40 × 10–2
11.1
6.45

Answer 13

not c.

Question 14

At a given temperature, 0.0664 mol N2O4(g) is placed in a 1.00 L flask. After reaching equilibrium, the concentration of NO2(g) is 6.1 × 10–3 M. What is Kc for the reaction below?
N2O4(g) 2 NO2(g)
3.7 ×10–5
1.4 ×10–4
5.9 × 10–4
9.6 × 10–2
1.8 × 103

Answer 14

c.

Question 15

A sample of solid NH4NO3 was placed in an evacuated container and then heated so that it decomposed explosively according to the following equation:
NH4NO3(s) N2O(g) + 2H2O(g)

At equilibrium the total pressure in the container was found to be 2.72 atm at a temperature of 500.°C. Calculate Kp.

1.64
0.822
2.98
80.5
0.745

Answer 15

c.

Question 16

Consider the formation of ozone by the following reaction.
3 O2(g) 2 O3(g)

Calculate the value of Kp, given that Kc = 2.5 × 10–29 at 298 K. (R = 0.08206 L⋅atm/mol ⋅ K)

1.0 × 10–30
2.1 × 10–30
2.5 × 10–29
3.3 × 10–28
6.1 ×10–28

Answer 16

not b.

Question 17

An aqueous mixture of phenol and ammonia has initial concentrations of 0.200 M C6H5OH(aq) and 0.120 M NH3(aq). At equilibrium, the C6H5O–(aq) concentration is 0.050 M. Calculate the equilibrium constant, K, for the reaction below.
C6H5OH(aq) + NH3(aq) C6H5O– + NH4+(aq)

0.10
0.24
2.1
4.2
4.8

Answer 17

b.

Question 18

Consider the following equilibria.
PbBr2(s) Pb2+(aq) + 2 Br–(aq) K1 = 6.6 × 10–6
Pb(OH)2(s) Pb2+(aq) + 2 OH–(aq) K2 = 1.4 × 10–15
Determine the equilibrium constant, Kc, for the reaction below.
PbBr2(s) + 2 OH–(aq) Pb(OH)2(s) + 2 Br–(aq)

9.2 × 10–21
2.1 × 10–10
6.6 × 10–6
4.7 × 109
1.1 × 1020

Answer 18

not b.