Chapter 15 Homework

Question 1

Methanol, a potential replacement for gasoline as an automotive fuel, can be made from H2 and CO by the reaction CO(g) + 2H2(g) <==> CH3OH(g). How will this reaction be affected if the volume of the container is reduced?

Answer 1

More methanol will be formed.

Question 2

In a reaction, the equilibrium constant for the forward reaction is Kf and the equilibrium constant of the backward reaction is Kb. What is the relationship between Kf and Kb?

Answer 2

Kf = 1 / Kb

Question 3

In the following reaction,
COCl2(g) <==> CO(g) + Cl2(g)
the equilibrium constant Kc is 0.00463 at 527 degrees C. If the initial pressure of COCl2 (reactant) is 0.76 atm, what are the partial pressures of CO and Cl2 at equilibrium

Answer 3

0.48 atm each

Question 4

The equilibrium constant in terms of partial pressure, Kp, is related to the equilibrium constant in terms of concentration, Kc, by which of the following expressions?

Answer 4

Kc = Kp / (RT)Δn

Question 5

For the following reaction in which ammonia is synthesized, the equilibrium constant Kc, is 0.65 at 375 degrees C.
N2(g) + 3H2(g) -> 2NH3(g)
Initial concentrations of H2, N2, and NH3 are 0.76 M, 0.60 M, and 0.48M, respectively. In which direction will the reaction proceed to reach equilibrium

Answer 5

right to left

Question 6

For the Haber-Bosch process, the value of the equilibrium constant is 610^5 at 35 degrees C and 410^-4 at 367 degrees C. This means that ______
N2(g) + 3H2(g) <==> 2NH3(g)

Answer 6

the system gives off heat during the synthesis of ammonia.

Question 7

C(s) + CO2(g) <==> 2CO(g)
When this system is at equilibrium at 700 degrees C in a 1L container, there are 0.2 mol CO, 0.4 mol CO2, and 0.8 mol C. When the system is cooled at 600 degrees C, an additional 0.04 mol C forms. Calculate the equilibrium constant at 700 degrees C and again at 600 degrees C.

Answer 7

Kc = 0.1 at 700 °C and Kc = 0.033 at 600 °C

Question 8

Suppose that you have 45 L of components in a flask. The components include 1.2 mol N2, 2.5 mol H2, and 1.1 mol NH3. If the equilibrium equation is N2(g) + 3H2(g) <==> 2NH3(g) (where Keq = 0.50 at 400 degrees C), which statement is NOT correct?

Answer 8

[ NH3 ] = 0.024 mol / L, but at equilibrium, this concentration will have increased.

Question 9

Suppose that you have a flask containing CH3 at a partial pressure of 2.3, H2O at a partial pressure of 1.5, CO at a partial pressure of 2.8, and H2 at a partial pressure of 0.3.
What is the reaction quotient for this reaction?
CH4(g) + H2O(g) <==> CO(g) + 3H2(g)

Answer 9

0.022

Question 10

The initial concentrations of each component are indicated by the I values. What are the four S values for this reaction? 
CH4(g) + H2O(g) <==> CO(g) + 3H2(g)
Kp = 1.8*10^-7?
CH4 0.0 atm
H2O 0.95 atm
CO 1.2 atm
3H2 3.9 atm

Answer 10

1.2 atm; 2.15 atm; 0 atm; 0.3 atm

Question 11

For the reaction N2O4(g) <==> 2NO2(g), Kp = 3.5

If the total pressure at equilibrium is 2.68 atm, what are the final partial pressure for the system at equilibrium?

Answer 11

1.78 atm (NO2 ); 0.90 atm (N2O4 )

Question 12

Look at the following system.

PCl5(g) <==> PCl3(g) + Cl2(g)

Suppose that the equilibrium constant, KP, is 490 (at 340°C). If the partial pressure of PCl3 is 1.87 atm and the partial pressure of Cl2 is 0.29 atm, what is the partial pressure of PCl5?

Answer 12

0.0011 atm

Question 13

Hydrogen combines with iodine to produce hydrogen iodide, HI.
H2(g) = I2(g) <==> 2HI(g)
Suppose that at equilibrium you had the following partial pressures:
PH2 = 0.537 atm, PI2 = 0.163 atm, and PHI = 2.85 atm. Suppose you then change the PI2 to 1.25atm. What would the final partial pressures be at equilibrium if x is is the change in concentration for I2?

Answer 13

PH2 = (0.537-x) atm
PI2 = (1.25-x) atm
PHI = (2.85+x) atm

Question 14

Look at the reaction below
H2(g) + I2(g) <==> 2HI(g), For this reaction, Kp = 92.6. Initially, PH2 = 0.105 atm, PI2 = 0.224 atm, and PHI = 2.97 atm. You add H2 until its pressure reaches 2.51 atm. Let x equal the change in partial pressure of H2. What are the final equilibrium concentrations of all three components?

Answer 14

PHI = 3.31 atm
PH2 = 2.34 atm
PI2 = 0.054 atm

Question 15

Look at the following reaction of solutions that we examined in the lesson.

Cp2(aq) <==> 2Cp(aq)

(Cp indicates cyclopentadiene, and Cp2 indicates dicylcopentadiene)

Which statement about this reaction is not true?

Answer 15

Decreasing the volume of the system will force the system to make more molecules. This is accomplished by the reverse reaction, in which Cp → Cp2.

Question 16

Which change in volume will cause the value of Q to increase by a factor of 3 for this reaction?
N2O4(g) <==> 2NO2(g)

Answer 16

decreasing the volume by a factor of 3

Question 17

Look at the following equilibrium reaction.

2BrCl(g) <==> Br2(g) + Cl2(g)

Suppose that the volume of the container is doubled. Which statement for this event is not correct?

Answer 17

The value for Q would decrease by a factor of 2

Question 18

Look at the plot for Keq vs. temperature for an exothermic reaction. Which statement about this plot is correct?

Answer 18

Any change in temperature is a stress to the system.