11. The Law of Mass Action states that:

• A) Rate of a reaction depends on temperature only
• B) Rate of reaction depends on concentration of reactants
• C) Rate of reaction depends on pressure
• D) Equilibrium constant is unaffected by concentration
• Answer: B

12. In a reversible chemical reaction at equilibrium, the rate of the forward reaction is:

• A) Zero
• B) Greater than the reverse reaction
• C) Less than the reverse reaction
• D) Equal to the reverse reaction
• Answer: D

13. Which of the following expressions represents the equilibrium constant (Kc) for the reaction ( aA + bB \rightleftharpoons cC + dD )?

• A) ( K_c = \frac{[A]^a[B]^b}{[C]^c[D]^d} )
• B) ( K_c = \frac{[C]^c[D]^d}{[A]^a[B]^b} )
• C) ( K_c = [A][B] – [C][D] )
• D) ( K_c = [C][D] \times [A][B] )
• Answer: B

14. If the equilibrium constant (Kc) for a reaction is very large, it indicates that:

• A) The reactants are favored at equilibrium
• B) The reaction hardly proceeds
• C) Products are favored at equilibrium
• D) The reaction has no equilibrium
• Answer: C

15. At equilibrium, the concentration of reactants and products:

• A) Continues to change
• B) Becomes zero
• C) Remains constant
• D) Becomes equal
• Answer: C

16. The units of an equilibrium constant (Kc) for a reaction are:

• A) Always in M
• B) Always in mol/L
• C) Depend on the balanced equation
• D) Always unitless
• Answer: C

17. In the reaction ( N_2 + 3H_2 \rightleftharpoons 2NH_3 ), the expression for ( K_c ) is:

• A) ( K_c = \frac{[NH_3]}{[N_2][H_2]^3} )
• B) ( K_c = \frac{[N_2][H_2]^3}{[NH_3]^2} )
• C) ( K_c = \frac{[NH_3]^2}{[N_2][H_2]^3} )
• D) ( K_c = [N_2][H_2]^3 \times [NH_3]^2 )
• Answer: C

18. If Kc > 1, then at equilibrium:

• A) Reactants are favored
• B) Products are favored
• C) Neither reactants nor products are favored
• D) Both are equal in concentration
• Answer: B

19. If a system at equilibrium is disturbed, it will shift to:

• A) Minimize the disturbance
• B) Maximize reactants
• C) Maximize products
• D) Remain unaffected
• Answer: A

20. For a given reaction, if the concentration of reactants increases, the equilibrium will:

• A) Shift to the right
• B) Shift to the left
• C) Remain unchanged
• D) Reach a new equilibrium
• Answer: A