Q: For the reaction $$2\text{N}_2\text{O}_5(g) \rightleftharpoons 4\text{NO}_2(g) + \text{O}_2(g)$$, which is the correct expression for the equilibrium constant $$K_c$$?

$$K_c = \dfrac{[\text{NO}_2]^4[\text{O}_2]}{[\text{N}_2\text{O}_5]^2}$$

Q: For the reaction $$\text{CO}_2(g) + \text{CF}_4(g) \rightleftharpoons 2\text{COF}_2(g)$$, write the correct $$K_c$$ expression.

$$K_c = \dfrac{[\text{CO}_2][\text{CF}_4]}{[\text{COF}_2]^2}$$

Q: A reaction mixture contains 0.22 M CH$$_4$$, 0.67 M CO$$_2$$, and 1.3 M H$$_2O $$for the reaction $$4\text{CuO}(s) + \text{CH}_4(g) \rightleftharpoons \text{CO}_2(g) + 4\text{Cu}(s) + 2\text{H}_2\text{O}(g)$$ with $$K_c = 1.10. $$What is the value of the reaction quotient $$Q$$?

$$Q = \dfrac{[\text{CO}_2][\text{H}_2\text{O}]^2}{[\text{CH}_4]} = \dfrac{0.67 \times (1.3)^2$}{0.22}$$

Q: For the reaction $$\text{Br}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{IBr}(g)$$ with $$K_p = 322$$, if the equilibrium partial pressures of Br$$_2$$ and I$$_2$$ are 0.315 atm and 0.129 atm, what is the equilibrium partial pressure of IBr?

$$[\text{IBr}] = \sqrt{K_p \times [\text{Br}_2][\text{I}_2]}$$

Question 1

Which of the following best describes a chemical system at equilibrium?

Accepted Answer

The rate of the forward and reverse reactions are equal.

Question 2

For the reaction $$2	ext{N}_2	ext{O}_5(g) ightleftharpoons 4	ext{NO}_2(g) + 	ext{O}_2(g)$$, which is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \dfrac{[	ext{NO}_2]^4[	ext{O}_2]}{[	ext{N}_2	ext{O}_5]^2}$$

Question 3

If the equilibrium constant $$K$$ for a reaction is much greater than 1, what does this indicate about the reaction at equilibrium?

Accepted Answer

The reaction is product-favored at equilibrium.

Question 4

Given the reaction $$A(g) + B(g) \rightleftharpoons AB(g)$$ with $$K_c = 0.24$$, what is the equilibrium constant for $$2AB(g) \rightleftharpoons 2A(g) + 2B(g)$$?

Accepted Answer

$$K_c = 17 ($$since $$K_{reverse} = 1/(K_{forward})$$ and squared for doubling coefficients)

Question 5

For the reaction $$2	ext{CO}(g) ightleftharpoons 	ext{CO}_2(g) + 	ext{C}(s)$$, which of the following is true about the equilibrium expression?

Accepted Answer

The concentration of solid carbon does not appear in the equilibrium expression.

Question 6

For the reaction $$	ext{CO}_2(g) + 	ext{CF}_4(g) ightleftharpoons 2	ext{COF}_2(g)$$, write the correct $$K_c$$ expression.

Accepted Answer

$$K_c = \dfrac{[	ext{CO}_2][	ext{CF}_4]}{[	ext{COF}_2]^2}$$

Question 7

A reaction mixture contains 0.22 M CH$$_4$$, 0.67 M CO$$_2$$, and 1.3 M H$$_2O $$for the reaction $$4	ext{CuO}(s) + 	ext{CH}_4(g) ightleftharpoons 	ext{CO}_2(g) + 4	ext{Cu}(s) + 2	ext{H}_2	ext{O}(g)$$ with $$K_c = 1.10. $$What is the value of the reaction quotient $$Q$$?

Accepted Answer

$$Q = \dfrac{[	ext{CO}_2][	ext{H}_2	ext{O}]^2}{[	ext{CH}_4]} = \dfrac{0.67 	imes (1.3)^2$}{0.22}$$

Question 8

For the reaction $$	ext{Br}_2(g) + 	ext{I}_2(g) ightleftharpoons 2	ext{IBr}(g)$$ with $$K_p = 322$$, if the equilibrium partial pressures of Br$$_2$$ and I$$_2$$ are 0.315 atm and 0.129 atm, what is the equilibrium partial pressure of IBr?

Accepted Answer

$$[	ext{IBr}] = \sqrt{K_p 	imes [	ext{Br}_2][	ext{I}_2]}$$

Question 9

Which of the following changes will shift the equilibrium of $$	ext{N}_2(g) + 3	ext{H}_2(g) ightleftharpoons 2	ext{NH}_3(g) to $$the right?

Accepted Answer

Increasing the pressure by decreasing the volume.

Question 10

For the reaction $$A(aq) + 2B(aq) \rightleftharpoons C(aq) + 3D(aq)$$, if the initial concentrations are $$[A]_0 = 1.0 M$$, $$[B]_0 = 1.0 M$$, and $$K = 1.0$$, what is the equilibrium concentration of D if $$x is $$the change in [A]?

Accepted Answer

$$[D]_{eq} = 3x$$

Question 11

Which of the following statements about Le Chatêlier’s Principle is correct?

Accepted Answer

If more product is added, the system shifts left.

Question 12

For the endothermic reaction $$	ext{PCl}_5(g) ightleftharpoons 	ext{PCl}_3(g) + 	ext{Cl}_2(g)$$, what happens if the temperature is decreased?

Accepted Answer

The equilibrium shifts to the left.

Question 13

Which of the following is true about the effect of adding an inert gas to a reaction at equilibrium in a constant volume container?

Accepted Answer

There is no shift in the equilibrium position.

Question 14

For the reaction $$	ext{CH}_3	ext{CO}_2	ext{H}(aq) + 	ext{H}_2	ext{O}(l) ightleftharpoons 	ext{H}_3	ext{O}^+(aq) + 	ext{CH}_3	ext{CO}_2^-(aq)$$ with $$K = 1.8 	imes 10$$^{-5}$$ and initial acetic acid concentration of 0.67 M, what is the equilibrium concentration of $$	ext{H}_3	ext{O}^+$$?

Accepted Answer

$$[	ext{H}_3	ext{O}^+] = 0.0035 M$$

Question 15

If $$K_c = 2.50 	imes 10$$^{-5}$$ for A$$ ightleftharpoons 2B$$ and $$[A]_0 = 1.00$$ M, $$[B]_0 = 0.00$$ M, what is the equilibrium concentration of A$ (rounded to two decimal places)?

Accepted Answer

$$[A]_{eq} \approx 0.999 M$$

Question 16

For the reaction $$aA(g) + bB(g) \rightleftharpoons cC(g) + dD(g)$$, the relationship between $$K_p$$ and $$K_c is $$given by:

Accepted Answer

$$K_p = K_c (RT$$)^{\Delta n}$$

Question 17

Which of the following best describes dynamic equilibrium in a closed bottle of water as shown in the vaporization diagram?

Accepted Answer

The rate of evaporation equals the rate of condensation.

Chapter 16: Chemical Equilibrium – Principles, Calculations, and Applications

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