Chapter 15

Consider the following equilibrium reaction: PCl3(g) + Cl2(g) ⇔ PCl5(g) Kc = 96.2 The equilibrium constant for the decomposition of PCl5(g) to PCl3(g) and Cl2(g) is:

)

In the reaction: 2 N2O(g) + N2H4(g) ⇔ 3 N2(g) + 2 H2O(g), one starts with 0.10 mol N2O and 0.25 mol N2H4 in a 10.0 L container. If there are 0.06 mol N2O at equilibrium, how many moles of N2 are present?

) 0.06

Kp for the following reaction at 25.0 °C. SbCl5(g) ⇔ SbCl3(g) + Cl2(g) Kc = 2.51 × 10-2

) 0.614

At a certain temperature, Kc = 0.0500 and △H = +39.6 kJ for the reaction below. 2MgCl2(s) + O2(g) ⇌ 2MgO(s) + 2Cl2(g) Calculate Kc for the reaction MgO(s) + Cl2(g) ⇌ MgCl2(s) + O2(g) and indicate whether the value will be larger or smaller at a lower temperature.

) 4.47, larger

For the reaction: 3 Fe(s) + 4 H2O(g) ⇔ Fe3O4(s) + 4 H2(g) what is the effect of adding Fe(s)?

) There is no change.

For the reaction 2 A(g) ⇔ B(g) + C(g), Kc = 1.25 at 300 K. If a 1.00 L mixture contains 0.619 mol A, 0.693 mol B, and 0.689 mol C at 300 K, will the mixture be in equilibrium? If not, in what direction will a net reaction occur?

) Yes, at equilibrium

All of the following may shift the position of a reaction at equilibrium EXCEPT

) homogeneous catalyst

Consider the equilibrium system: N2O4 ⇔ 2 NO2(g) for which Keq = 0.1134 at 25 °C and △H°rxn = 58.03 kJ/mol. Assuming that the total pressure inside the container is 10 atm at equilibrium and that initially only N2O4 was present inside the container, compute at equilibrium.

...

Consider the following equilibrium. A(g) + 3B(g) ⇌ 2C(g) If the initial concentrations are [A(g)] = 1.00 M, [B(g)] = 3.00 M, and [C(g)] = 0, at equilibrium it is found that [C(g)] = 0.980 M. Calculate Kc for this reaction.

...

Consider the following reaction occurring at 960 K: CO2(g) + H2(g) ⇔ CO(g) + H2O(g) At equilibrium, the concentrations of reactants and products are: [CO2] = 0.0400 M, [H2] = 0.0220 M, [CO] = 0.0240 M, and [H2O] = 0.0190 M. This equilibrium is perturbed by adding CO2(g) to the system such that when a new equilibrium is reached, the concentration of CO2 is 0.050 M. What is the concentration of H2(g) at this equilibrium?

...

Consider the following reaction: POCl3(g) ⇔ POCl(g) + Cl2(g) Kc = 0.450 A sample of pure POCl3(g) was placed in a reaction vessel and allowed to decompose according to the above reaction. At equilibrium, the concentrations of POCl(g) and Cl2(g) were each 0.150 M. What was the initial concentration of POCl3(g)?

...

Consider the following reversible reaction: POCl3(g) ⇔ POCl(g) + Cl2(g) Kc = 0.450 The following initial amounts of reactants and products were mixed: [POCl3] = 0.750 M, [POCl] = 0.550 M, and [Cl2] = 0.150 M. What is the equilibrium concentration of POCl?

...

For the decomposition of ammonium carbamate NH4(NH2CO2)(s) ⇌ 2NH3(g) + CO2(g) Kp = 0.0596 at a certain temperature. A solid sample of ammonium carbamate is introduced into an evacuated container and at equilibrium some solid remains in the container. What is the total pressure in the container?

...

For the reaction 2 NO(g)⇔ N2O4(g) Kp equals:

...

For the reaction: 3 Fe(s) + 4 H2O(g) ⇔ Fe3O4(s) + 4 H2(g) Write the expression for Kp.

...

For the reaction: PCl3(g) + Cl2(g) ⇔ PCl5(g) at 85 °C, Kp = 1.19 If one starts with 2.00 atm pressure of PCl3, 1.00 atm pressure of Cl2 and no PCl5, what is the partial pressure of PCl5(g) at equilibrium?

...

For the reaction: 2 NO2(g) ⇔ 2 NO(g) + O2(g), the partial pressure of O2(g) at equilibrium is 0.3500 atm. Ptotal = 1.0866 atm. What is Kp for this reaction?

...

Keq = 1.78 at 250 °C for the decomposition reaction of PCl5(g) ⇔ PCl3(g) + Cl2(g). Calculate the percentage of PCl5 that dissociates if 0.05 mole of PCl5 is placed in a closed vessel at 250 °C and at 2.00 atm pressure.

...

What is the equilibrium constant expression for: 4 NH3(g) + 5 O2(g) ⇌ 4 NO(g) + 6 H2O(g)

...

Write the equilibrium constant expression for the following reaction: 2 KI(aq) + H2O2(aq) ⇔ 2 KOH(aq) + I2(aq)

...

Write the equilibrium constant expression for the following reaction: 6 CO2(g) + 6 H2O(l) ⇔ C6H12O6(s) + 6 O2(g)

...

Write the equilibrium constant expression for the following reaction: N2(g) + 3 H2(g) ⇌ 2 NH3(g)

...

Write the equilibrium expression Kc for the reaction: sodium sulfite(aq) + chloric acid (aq) ⇔ sodium chlorite(aq) + sulfur dioxide(g) + water(l).

...

For CO2(g) + H2(g) ⇔ CO(g) + H2O(g), Kc = [CO][H2]/[CO2][H2], if there are 1.43 mols each of CO and H2, 0.572 mol H2 and 4.572 mols CO2, in a 4.0 L container at equilibrium, what is Kc?

0.782

For the reaction: PCl3(g) + Cl2(g) ⇔ PCl5(g) at 70.5 °C, Kp = 1.05. If one starts with 1.80 atm pressure of PCl3(g), 1.72 atm pressure of Cl2(g), and no PCl5(g), what is the partial pressure of PCl5(g) at equilibrium?

0.827 atm

) A mixture containing 0.392 M A(g) and 0.452 M B(g) is allowed to come to equilibrium at 300 K. The reaction 3 A(g) + 2 B(g) ⇔ C(g) + D(g) occurs. At equilibrium, [C] = 0.00128 M. What is the value of Kc?

1.39 × 10-4

What is the value for Kc for the reaction below if the equilibrium concentrations are [N2] = 0.025, [H2] = 0.0013 and [NH3] = 0.028 for the following reaction?

1.4 × 107

What is the value for Kc if [CO] = 0.025, [H2] = 0.013 and [CH3OH] = 0.0028 for the following reaction?

1.5 × 10-3

) Two moles of NH3 are initially present for the reaction: 2 NH3(g) ⇔ N2(g) + 3 H2(g) At equilibrium there is 1.00 NH3. How many mols of H2 are present at equilibrium?

1.50

For the reaction below CO(g) + 2H2(g) ⇌ CH3OH(g) the equilibrium concentrations at 483 K are [CO(g)] = 0.0753 M, [H2(g)] = 0.151 M, and [CH3OH(g)] = 0.0247 M. Calculate the value of Kc.

14.4

Given that the equilibrium concentrations of [N2] = 0.035 M, [C2H2] = 0.057 M, and [HCN] = 6.8 × 10-4 M, find the value of the equilibrium constant expression for the reaction: N2(g) + C2H2(g)

2.3 × 10-4

) Consider the following equation: N2O4(g) ⇔ 2 NO2(g) Kc = 5.8 × 10-3 If the initial concentration of N2O4(g) = 0.040 M and the initial concentration of NO2(g) is 0 M, what is the equilibrium concentration of N2O4(g)?

2.3 × 10-6 M

Given the following: I) N2O(g) + 1/2 O2(g) ⇔ 2NO(g) Kc = 1.7 × 10-13 II) N2(g) + O2(g) ⇔ 2NO(g) Kc = 4.1 × 10-31 Find the value of the equilibrium constant for the following equilibrium reaction: N2(g) + 1/2 O2(g) ⇔ N2O(g)

2.4 × 10-18

) Consider the following gas phase reaction at 25 °C. N2(g) + C2H2(g) ⇔ 2 HCN(g) 1.600 mol N2(g) and 1.750 mol C2H2(g) are placed in a 1.000 L vessel and the mixture is allowed to react. At equilibrium, there are 1.587 mol N2(g) in the mixture. What is Kc for this reaction at 25 °C?

2.5 × 10-4

A mixture containing 0.0392 M A(g) and 0.0452 M B(g) is allowed to come to equilibrium at 300 K.

20.4

Given the following reactions, 2PCl3(g) ⇌ 2P(g) + 3Cl2(g) Kc = 0.0667 PCl3(g) + Cl2(g) ⇌ PCl5(g) Kc = 4.0 calculate Kc for the reaction below. 2P(g) + 5Cl2(g) ⇌ 2PCl5(g)

240

Which of the following equilibrium constants-reaction type is INCORRECT?

3.2 × 103 equilibrium reaction-more reactants than products at equilibrium.

For the decomposition of SO3(g), Kc = [SO2]2[O2]/[SO3]2, at equilibrium, there are 0.090 mol SO2, 0.110 mol O2, 0.100 mol SO3 in a 25.0-L container. What is the value of Kc?

3.6 × 10-3

For the formation of NO, Kc = [NO]2/[NO]2[O2]. At equilibrium in a 2.50 L container, there are 3.00 mol NO, 4.00 mol O2 and 22.0 mol NO2. The value of Kc is:

33.6

For which of the following reactions does Kp = Kc?

3Fe(s) + 4H2O(g) ⇌ Fe3O4(s) + 4H2(g)

For the reaction: H2(g) + I2(g) ⇔ 2 HI(g), Kc = 92.0 When equilibrium concentrations of HI and I2 are [HI] = 0.115 M and [I2] = 0.250 M, the equilibrium concentration of [H2] is:

5.75 × 10-4 M

For 2 NO2(g) ⇔ N2O4(g), Kc = [N2O4]/[NO2]2. At equilibrium there are 0.0270 mol N2O4 and 0.450 mol NO2 in a 50.0-L container. What is Kc?

6.67

) Consider the following reaction at a certain temperature. 2SO3(g) ⇌ 2SO2(g) + O2(g) When the initial concentration of SO3(g) is 0.128 M, at equilibrium the concentration of oxygen gas is found to be 0.0130 M. Calculate Kc for this reaction.

8.45 x 10-4

Choose the correct statement about a container in which the chemical equilibrium is established: 2 SO2(g) + O2(g) → 2 SO3(g) + heat

A decrease in the volume will decrease the amount of SO2 present.

Choose the INCORRECT statement.

A reversible chemical reaction is one in which equilibrium is never established due to the constant decomposition of the products.

Choose the correct statement about the equilibrium

Conducting the reaction under high pressures will increase the yield of ammonia

) Write the equilibrium constant expression for the reaction: 3 Sn(s) + 4 HNO3(aq) + H2O(l) ⇔ 3 H2SnO3(s) + 4 NO(g)

Kc =

For the following chemical equilibrium, Kp = 4.6 × 10-14 at 25 °C, find the value of Kc for this reaction at 25 °C. 2 Cl2(g) + 2 H2O(g) ⇔ 4 HCl(g) + O2(g)

Kc = 1.9 × 10-15

Consider the following hypothetical equilibrium reaction: A2(g) + B2(g) ⇔ 2AB(g) where Kc = The equilibrium constant for the reaction: 2 A2(g) + 2 B2(g) ⇔ 4 AB(g) is:

Kc2

What is the relationship between Kp and Kc for the reaction below?

Kp = Kc(RT)-3

) For the reaction: 2 SO2(g) + O2(g) ⇔ 2 SO3(g), Kc = 6.9 × 1024 at 25 °C. If a reaction vessel is filled with these gases, such that [SO2] = 6.0 M, [O2] = 6.0 M and [SO3] = 6.0 M, in which direction will the reaction proceed?

The reaction proceeds to the right

For the reaction: 3 Fe(s) + 4 H2O(g) ⇔ Fe3O4(s) + 4 H2(g) what is the effect on equilibrium of increasing temperature of an exothermic reaction?

The reaction shifts to the left.

For the reaction: 3 Fe(s) + 4 H2O(g) ⇔ Fe3O4(s) + 4 H2(g) what is the effect of removing H2?

The reaction shifts to the right.

2.5 moles H2O and 100 g of C are placed in a 50-L container. At equilibrium for the reaction C(s) + H2O(g) ⇔ CO(g) + H2(g), [H2] = 0.040 M. Which of the following is true?

[H2O] = 0.010 M

0.75 mol of N2 and 1.20 mol of H2 are placed in a 3.0 liter container. When the reaction N2(g) + 3H2(g) ⇔ 2 NH3(g) reaches equilibrium, [H2] = 0.100 M. Which of the following is true?

[NH3] = 0.200

Which of the following substances present in the chemical reaction would NOT be included in the equilibrium constant expression?

all of these

For the following reaction O2(g) ⇌ 2O(g) what conditions favor production of oxygen atoms?

high temperature and low pressure

Consider the following chemical reaction at equilibrium: 2 Cl2(g) + 2 H2O(g) ⇔ 4 HCl(g) + O2(g)

increasing the volume of the mixture

For the reaction CO(g) + 3 H2(g) → H2O(g) + CH4(g), Kc = 190 at 1000 K. If a vessel is filled with these gases such that the initial concentrations are [CO] = 0.036M, [H2] = 0.045, [H2O] = 0.020, and [CH4] = 0.031, in which direction will a reaction occur and why?

it is at equilibrium

Consider the following reaction. C(s) + H2O(g) ⇌ CO(g) + H2(g) At equilibrium at a certain temperature, [H2O(g)] = 0.12 M, and [CO(g)] = [H2(g)] = 1.2 M. If suddenly these concentrations are increased by 0.50 M, which of the following is true?

more products are formed

What will happen to the equilibrium in the reaction 2 A(g) ⇔ B(g) + C(g), Kc = 1.25 at 300 K if a catalyst is added?

no change, catalyst only changes the rate

Which factor influences the value of the equilibrium constant for a reversible reaction?

raising the temperature

For a reaction, the reaction quotient, Qc > K, the reaction:

shifts to the left

Consider the reaction: CH4(g) + 4 Cl2(g) ⇔ CCl4(l) + 4 HCl(g) ΔH° -398 kJ/mol The equilibrium is displaced to the right if

some carbon tetrachloride is removed

Keq is constant except when one varies the:

temperature of the reaction

In a reaction at equilibrium involving only gases, a change in pressure of the reaction mixture shifts the position of equilibrium only when:

the moles of gas are not equal on the two sides of the equation.

In a reaction at equilibrium involving only gases, a pressure change will shift the reaction only when:

the number of molecules on one side is greater than the number on the other side of the balanced equation

For the reaction: CH4(g) + 2H2O(g) ⇔ CO2(g) + 4H2(g) ΔH° = +190 kJ add H2(g):

the reaction reacts to the left.

For the reaction: CH4(g) + 2 H2O(g) ⇔ CO2(g) + 4 H2(g) ΔH° = +190 kJ when CH4 is added:

the reaction reacts to the right

For the reaction: CH4(g) + 2 H2O(g) ⇔ CO2(g) + 4 H2(g) ΔH° = +190 kJ raise the temperature to 1200 K:

the reaction reacts to the right.

Consider the reaction: 2SO2(g) + O2(g) ⇔ 2SO3(g) ΔH° = -196.6 kJ/mol

the temperature is raised

For the reaction: CH4(g) + 2H2O(g) ⇔ CO2(g) + 4H2(g) ΔH° = +190 kJ add N2(g) at constant volume:

the ΔH° increases

For the reaction: CH4(g) + 2 H2O(g) ⇔ CO2(g) + 4 H2(g) ΔH° = +190 Kj when catalyst is added:

there is no change, catalyst changes rate only.

For the reaction 2 SO2 (g) + O2 (g) → 2 SO3 (g), Kc = 2.8 ⊥ 102 at 1000 K. If a vessel is filled with these gases such that the initial concentrations are [SO2] = 0.025, [O2] = 0.035, and [SO3] = 0.046, in which direction will a reaction occur and why?

toward products because Q = 96

For the reaction PCl5 (g) → PCl3 (g) + Cl2 (g) Kc = 0.0454 at 261°C. If a vessel is filled with these gases such that the initial concentrations are [PCl5] = 0.25M, [PCl3] = 0.20 M, and [Cl2] = 2.25 M, in which direction will a reaction occur and why?

toward reactants because Q = 1.8

For the reaction CO(g) + 3 H2(g) → H2O(g) + CH4(g) , Kc = 190 at 1000 K. If a vessel is filled with these gases such that the initial concentrations are [CO] = 0.025, [H2] = 0.045, [H2O] = 0.025, and [CH4] = 0.046M, in which direction will a reaction occur and why?

toward reactants because Q = 350

) According to Le Chatelier's Principle

when an equilibrium system is stressed, the system reacts to offset the stress

) A mixture, containing 0.0750 M HCl(g) and 0.0330 M O2(g) is allowed to come to equilibrium at 480 °C. 4HCl(g) + O2(g) ⇔ 2Cl2(g) + 2H2O(g) At equilibrium [Cl2] = 0.030 M. What is the value of Kc?

...

) Consider the equilibrium system: N2O4 ⇔ 2NO2(g) for which Keq = 0.1134 at 25 °C and △H°rxn = 58.03 kJ/mol. Assuming that the total pressure inside the container is 10 atm at equilibrium and that initially only N2O4 was present inside the container, compute at equilibrium.

...

) For the reaction: 3 Fe(s) + 4 H2O(g) ⇔ Fe3O4(s) + 4 H2(g) write the expression for Kc in terms of Kp

...

4.000 mol chlorine and 2.000 mol bromine were placed in a 50.0 L container and kept at 293 K until equilibrium was achieved for the reaction: Br2(l) + Cl2(g) ⇔ 2 BrCl(g) At the point of equilibrium there were 82.63 g of Br2(ℓ). Determine the total pressure in the 50.0 L container at equilibrium.

...

4.000 mol chlorine and 2.000 mol bromine were placed in a 50.0 L container and kept at 293 K until equilibrium was achieved for the reaction: Br2(l) + Cl2(g) ⇔ BrCl(g) At the point of equilibrium there were 82.63 g of Br2(l). Compute the value of Kc for this reaction.

...

At 25 °C, the pH of pure water is:

...

At 35 °C, Kp = 0.315 for the reaction N2O4 ⇔ 2 NO2(g), if the initial pressure of NO2(g) in a container is 3.00 atm, what is the equilibrium pressure of N2O4(g)?

...

Consider the equilibrium system: N2O4 ⇔ 2 NO2(g) for which Keq = 0.1134 at 25 °C and △H°rxn = 58.03 kJ/mol. Assume that 1 mole of N2O4 and 2 moles of NO2 are introduced into a 5.0 liter container. What will be the equilibrium value of [N2O4]?

...

Consider the equilibrium system: N2O4 ⇔ 2 NO2(g) for which Keq = 0.1134 at 25 °C and △H°rxn = 58.03 kJ/mol. Assume that 1 mole of N2O4 and 2 moles of NO2 are introduced into a 5.0 liter container. What will be the equilibrium value of [N2O]?

...

Consider the equilibrium system: N2O4 ⇔ 2 NO2(g) for which Keq = 0.1134 at 25 °C and △H°rxn = 58.03 kJ/mol. Assuming that the total pressure inside the container is 1.00 atm at equilibrium and that initially only N2O4 was present inside the container, compute at equilibrium.

...

Consider the equilibrium system: N2O4 ⇔ 2 NO2(g) for which Keq = 0.1134 at 25 °C and △H°rxn = 58.03 kJ/mol. Assuming that the total pressure inside the container is 1.00 atm at equilibrium and that initially only N2O4 was present inside the container, compute at equilibrium. 78)

...

Consider the reaction: 4 HCl(aq) + MnO2(s) ⇔ Cl2(g) + 2 H2O(l) + MnCl2(aq)

H2O(l) is added

For the reaction; N2(g) + 3 H2(g) ⇌ 2 NH3(g), the equilibrium amount of NH3 will be increased by:

I, II

For the reaction: 2 Cl2(g) + 2 H2O(g) ⇔ 4 HCl(g) + O2(g), Kp = 6.4 × 10-6 at 500 K. If a fixed volume is filled with initial concentrations of these gases at 227 °C such that [Cl2] = 0.5 M, [H2O] = 0.40 M, [HCl] = 0.5 M, and [O2] = 0.015 M, in which direction will the reaction proceed?

The reaction proceeds to the left.