Question 1

Which statement best describes chemical equilibrium in a closed system?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

For the reaction $$aA + bB \rightleftharpoons cC + dD$$, what is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \dfrac{[C]^c [D]^d}{[A]^a [B]^b}$$

Question 3

Given the reaction $$2HI(g) ightleftharpoons H_2$(g) + I_2$(g)$$, if the initial concentration of $$HI is 2.00 M $$and at equilibrium $$[HI] = 1.87 	imes 10$$^{-1}$$ M, what is the value of K_c$?

Accepted Answer

$$K_c = \dfrac{[H_2$][I_2$]}{[HI]^2}$$

Question 4

For the reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$, if $$[$$N_2$$] = 2.00$$ M, $$[$$H_2$$] = 1.00$$ M, and $$[$$NH_3$$] = 0.500$$ M at equilibrium, what is the value of K_c$?

Accepted Answer

$$K_c = \dfrac{[NH_3$]^2}{[N_2$][H_2$]^3}$$

Question 5

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

Accepted Answer

The reaction favors the formation of products.

Question 6

For the reaction $$COCl_2(g$$) ightleftharpoons CO(g) + $$Cl_2(g$$)$$, if K_c$ for the forward reaction is 4.0$$ 	imes $$10^{-4}$$, what is $$K_c$$ for the reverse reaction?

Accepted Answer

$$K_c = 2.5 	imes 10$$^{3}$$

Question 7

Which of the following changes will shift the equilibrium of $$N_2O_4(g) \rightleftharpoons 2NO_2(g) to $$the right?

Accepted Answer

Increasing the temperature (reaction is endothermic)

Question 8

For the reaction $$N_2O_4(g) \rightleftharpoons 2NO_2(g) at $$equilibrium in a cylinder with a piston, what happens if the pressure is increased?

Accepted Answer

The equilibrium shifts to the left, producing more $$N_2O_4.$$

Question 9

Which statement about the effect of a catalyst on a chemical equilibrium is correct?

Accepted Answer

A catalyst speeds up both the forward and reverse reactions equally, but does not affect the position of equilibrium.

Question 10

For the reaction $$2HI(g) \rightleftharpoons H_2$(g) + I_2$(g)$$, if $$Q \u003c K_c$$, what will happen?

Accepted Answer

The reaction will shift to the right, forming more $$H_2$$ and $$I_2.$$

Question 11

For the reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$, what will happen if more N_2$ is added to the system at equilibrium?

Accepted Answer

The equilibrium will shift to the right, producing more $$NH_3.$$

Question 12

For the reaction $$Cl_2(g$$) \rightarrow 2Cl(g)$$, breaking the bond requires energy. Is this process endothermic or exothermic?

Accepted Answer

Endothermic, because energy is absorbed.

Question 13

For the reaction $$2H_2(g) + 2F_2(g) \rightleftharpoons 4HF(g)$$, what is the correct expression for $$K_c$$?

Accepted Answer

$$K_c = \dfrac{[HF]^4}{[H_2$]^2 [F_2$]^2}$$

Question 14

How are the equilibrium constants $$K_c$$ and $$K_p$$ related for a reaction involving gases?

Accepted Answer

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

Question 15

For the reaction $$N_2O_4(g) \rightleftharpoons 2NO_2(g)$$, $$K_c = 0.211 at 100$$°C. If $$[N_2O_4] = 0.00455 M $$and $$[NO_2$] = 0.0310 M$$, is the reaction at equilibrium?

Accepted Answer

No, because $$Q \u003e K_c$$; the reaction will shift to the left.

Question 16

Which of the following is true about a system at equilibrium?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 17

For the reaction $$CO(g) + Cl_2$(g) ightleftharpoons $$COCl_2$$(g)$$, if $$K_c = 4.0 	imes 10$$^{-4}$$ and $$[CO] = 3.0 	imes $$10^{-1}$$ mol/L, $$[Cl_2$] = 3.0 	imes 10$$^{-1}$$ mol/L, and $$[$$COCl_2$$] = 4.0 	imes $$10^{-3}$$ mol/L at equilibrium, what does the value of $$K_c$$ tell you about the extent of the reaction?

Accepted Answer

The reaction strongly favors reactants.

Question 18

Which of the following is a characteristic of a heterogeneous equilibrium?

Accepted Answer

Reactants and products are in different phases.

Chemical Equilibrium: Concepts, Calculations, and Applications

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