Chapter 6 : Chemical Equilibrium

Which is the correct statement for a chemical equilibrium?

• The rate of the forward reaction is the same as that of the reverse reaction.

• The total concentration of product equals that of reactants.

• The rate constant of forward reaction equals that of the reverse reaction.

• The product of equilibrium concentration of products and reactants equals to the Kc value.

A mixture of gases is allowed to reach equilibrium at 700^oC in a 12.0 L flask. At equilibrium, the

mixture contains 0.208 M SO₂, 1.12×10^-6 M O₂ and 0.725 M SO₃.

2SO₂(g) + O₂(g) ⇌ 2SO₃ (g)

What is the equilibrium constant, K_c?

• 9.22 x 10^-8

• 3.11 x 10⁶

• 1.08 x 10⁷

• 4.56 x 10⁸

The reaction of carbon and carbon dioxide reached equilibrium according to the equation,

C(s) + CO₂(g) ⇌ 2CO (g)

K_c = 0.122 at 1100 K

What is the value of K_p for this reaction?

• 0.035 atm

• 0.12 atm

• 11 atm

• 945 atm

In which the of the following equilibrium systems will the product concentration increase by using

higher pressure?

• N₂O₄(g) ⇌ 2NO₂(g)

• O₂(g) + C(s) ⇌ 2CO(g)

• SbCl₅(g) ⇌ SbCl₃(g) + Cl₂(g)

• 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

At 2000K, the equilibrium constant K_C for the reaction

N₂ (g) + O₂ (g) ⇌ 2NO (g)

is 4.0 x 10^-4. Determine the concentration of NO at equilibrium if given the concentration of N₂ and O₂

at equilibrium is 0.25M and 0.33M, respectively.

• 1.7 x 10^-5 M

• 5.7 X 10^-3 M

• 3.3 X 10^-5 M

• 6.8 X 10^-3 M

Which equilibrium is NOT affected by the change of total pressure of the system?

• NH₄Cl(s) ⇌ NH₃(g) + HCl(g)

• PCl₅(g) ⇌ PCl₃(g) + Cl (g)

• 6H₂O(l)+ 6CO₂(g) ⇌ C₆H₁₂O₆(s) + 6O₂ (g)

• 2PbS (s) + 3O₂ (g) ⇌ 2PbO(s) + 2SO₂ (g)

The endothermic reaction

2NO(g) + Br₂(g) ⇌ 2NOBr(g)

Has an equilibrium constant, K_P= 116.6 at 25^oC

Which of the statement below is NOT true?

• the equilibrium constant K_P for reverse reaction is 8.58 x 10^-3

• removing Br₂ from the reaction vessel decrease the K_P value

• the equilibrium constant K_C is 116.6 RT

• K_P increase as temperature increased

The expression for equilibrium constant, K_C for the reaction

2SO₂(g) + O₂(g) ⇌ 2SO₃(g) is

• K_C = [SO₂ ] [ O₂] / [SO₃]

• K_C = [SO₂]²[ O2] / [SO₃ ]²

• K_C = [SO₃ ] / [SO₂][ O₂]

• K_C = [SO₃]² / [SO₂ ]²[ O₂]

The equilibrium constant K_C for the reaction

N₂O₄(g) ⇌ 2NO₂(g)

is 0.212 at 100 ^oC. what is the value of K_P?

• 14.28

• 1.74

• 198.62

• 6.49

Which of the following statements is CORRECT about the reaction quotient, Q_c, and the equilibrium

constant, K_c?

• For the same reaction, K_c is larger than Q_c.

• For the same reaction, Q_c and K_c have the same value.

• The reaction mixture is richer in products if Q_c < K_c.

• The value of Q_c changes until it reaches the value of K_c at equilibrium.