Grade 11 : Chemistry - Equilibrium (Set 1)

Question 1

What characterizes a reversible chemical reaction when it reaches dynamic equilibrium?

Accepted Answer

B) The rate of the forward reaction equals the rate of the reverse reaction.

Answer

A) The concentrations of reactants and products become equal.

Answer

C) The chemical reaction stops completely in both directions.

Answer

D) The total mass of products exceeds the mass of reactants.

Question 2

Which of the following processes represents a physical equilibrium?

Accepted Answer

B) $H_2O(l) ightleftharpoons H_2O(g)$ at $100^\circ	ext{C}$ and 1 atm

Answer

A) $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$

Answer

C) $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$

Answer

D) $PCl_5(g) \rightleftharpoons PCl_3(g) + Cl_2(g)$

Question 3

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

Accepted Answer

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

Answer

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

Answer

C) $K_c = [C]^c [D]^d - [A]^a [B]^b$

Answer

D) $K_c = \frac{[A] + [B]}{[C] + [D]}$

Question 4

If the equilibrium constant for the forward reaction $A + B \rightleftharpoons C + D$ is $K_c = 4.0$, what is the equilibrium constant $K_c'$ for the reverse reaction $C + D \rightleftharpoons A + B$?

Accepted Answer

C) 0.25

Answer

A) 4.0

Answer

B) -4.0

Answer

D) 0.50

Question 5

Which equation correctly relates the pressure equilibrium constant $K_p$ to $K_c$ for a reversible gaseous reaction?

Accepted Answer

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

Answer

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

Answer

C) $K_p = K_c + RT \Delta n$

Answer

D) $K_p = \frac{K_c}{RT}$

Question 6

For the reaction $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$, what is the value of $\Delta n$ used in the equation $K_p = K_c (RT)^{\Delta n}$?

Accepted Answer

B) -2

Answer

A) +2

Answer

C) 0

Answer

D) +1

Question 7

In writing the expression for equilibrium constant $K_c$ of a heterogeneous reaction, which states of matter are omitted?

Accepted Answer

C) Pure solids and pure liquids

Answer

A) Gaseous components only

Answer

B) Solutes in aqueous solution

Answer

D) Gas mixtures

Question 8

What is the effect of adding a suitable catalyst to a system already at chemical equilibrium?

Accepted Answer

C) It speeds up both forward and reverse reactions equally without shifting equilibrium.

Answer

A) It increases the equilibrium yield of products.

Answer

B) It shifts the equilibrium position toward the reactants.

Answer

D) It increases the numerical value of $K_c$.

Question 9

According to Le Chatelier's principle, what happens when additional reactant is introduced into a system at equilibrium?

Accepted Answer

A) The system shifts in the forward direction to consume the added reactant.

Answer

B) The system shifts in the reverse direction to produce more reactant.

Answer

C) The equilibrium constant $K_c$ increases.

Answer

D) The system remains completely unaffected.

Question 10

For an endothermic reaction ($\Delta H > 0$), how does an increase in temperature affect the equilibrium constant $K_c$?

Accepted Answer

B) $K_c$ increases.

Answer

A) $K_c$ decreases.

Answer

C) $K_c$ remains unchanged.

Answer

D) $K_c$ becomes negative.

Question 11

If the reaction quotient $Q_c$ is less than the equilibrium constant $K_c$ ($Q_c < K_c$), in which direction will the net reaction proceed?

Accepted Answer

B) Net reaction proceeds in the forward direction (right).

Answer

A) Net reaction proceeds in the reverse direction (left).

Answer

C) The system is already at equilibrium.

Answer

D) No reaction occurs.

Question 12

According to the Brønsted-Lowry theory, how is an acid defined?

Accepted Answer

A) A proton ($H^+$) donor

Answer

B) A proton ($H^+$) acceptor

Answer

C) An electron-pair donor

Answer

D) A hydroxide ion ($OH^-$) donor

Question 13

What is the conjugate base of hydrochloric acid, HCl?

Accepted Answer

B) $Cl^-$

Answer

A) $H_2Cl^+$

Answer

C) $OH^-$

Answer

D) $H_3O^+$

Question 14

What is the pH of a 0.001 M strong acid HCl solution in water at 298 K?

Accepted Answer

C) 3

Answer

A) 1

Answer

B) 2

Answer

D) 4

Question 15

What is the numerical value of the ionic product of pure water ($K_w$) at 298 K?

Accepted Answer

B) $1.0 	imes 10^{-14}$

Answer

A) $1.0 	imes 10^{-7}$

Answer

C) $1.0 	imes 10^{-10}$

Answer

D) 7.0

Question 16

If an aqueous solution has a pH of 5 at 298 K, what is its pOH?

Accepted Answer

C) 9

Answer

A) 5

Answer

B) 7

Answer

D) 14

Question 17

What phenomenon describes the suppression of ionization of a weak electrolyte by adding a strong electrolyte containing a shared ion?

Accepted Answer

B) Common ion effect

Answer

A) Buffer action

Answer

C) Salt hydrolysis

Answer

D) Neutralization

Question 18

What is the correct solubility product constant ($K_{sp}$) expression for the dissolution equilibrium $BaSO_4(s) \rightleftharpoons Ba^{2+}(aq) + SO_4^{2-}(aq)$?

Accepted Answer

A) $K_{sp} = [Ba^{2+}][SO_4^{2-}]$

Answer

B) $K_{sp} = \frac{[Ba^{2+}][SO_4^{2-}]}{[BaSO_4]}$

Answer

C) $K_{sp} = [Ba^{2+}] + [SO_4^{2-}]$

Answer

D) $K_{sp} = [Ba^{2+}]^2 [SO_4^{2-}]$

Question 19

Which of the following aqueous combinations forms an acidic buffer solution?

Accepted Answer

B) $CH_3COOH$ and $CH_3COONa$

Answer

A) HCl and NaCl

Answer

C) NaOH and NaCl

Answer

D) $NH_4OH$ and $NH_4Cl$

Question 20

According to Lewis acid-base theory, a Lewis base is defined as a species that:

Accepted Answer

C) Donates an electron pair

Answer

A) Accepts a proton

Answer

B) Donates a proton

Answer

D) Accepts an electron pair

Grade 11 : Chemistry - Equilibrium (Set 1)