Grade 11 : Chemistry - Equilibrium (Set 2)

Question 1

Which statement best describes a dynamic chemical equilibrium in a closed system?

Accepted Answer

B) The rates of the forward and reverse reactions are equal.

Answer

A) The reaction has completely stopped.

Answer

C) The concentrations of reactants and products must be equal.

Answer

D) The volume of reactants is equal to the volume of products.

Question 2

What is the correct equilibrium constant expression ($K_c$) for the reaction: $ ext{N}_2(g) + 3 ext{H}_2(g) ightleftharpoons 2 ext{NH}_3(g)$?

Accepted Answer

C) $K_c = \frac{[	ext{NH}_3]^2}{[	ext{N}_2][	ext{H}_2]^3}$

Answer

A) $K_c = \frac{[	ext{N}_2][	ext{H}_2]^3}{[	ext{NH}_3]^2}$

Answer

B) $K_c = \frac{[2	ext{NH}_3]}{[	ext{N}_2][3	ext{H}_2]}$

Answer

D) $K_c = \frac{[	ext{NH}_3]}{[	ext{N}_2][	ext{H}_2]}$

Question 3

Why are pure solids and pure liquids omitted from the equilibrium constant expression ($K_c$)?

Accepted Answer

A) Their molar concentration (density divided by molar mass) remains constant.

Answer

B) They do not take part in chemical reactions.

Answer

C) Their equilibrium concentrations are always zero.

Answer

D) Their equilibrium constants are infinitely large.

Question 4

In the equation $K_p = K_c(RT)^{\Delta n_g}$, what is the value of $\Delta n_g$ for the reaction: $2 ext{SO}_2(g) + ext{O}_2(g) ightleftharpoons 2 ext{SO}_3(g)$?

Accepted Answer

D) -1

Answer

A) +1

Answer

B) +2

Answer

C) 0

Question 5

According to Le Chatelier's principle, what happens if additional $ ext{N}_2(g)$ is added to the system: $ ext{N}_2(g) + 3 ext{H}_2(g) ightleftharpoons 2 ext{NH}_3(g)$ at constant volume?

Accepted Answer

B) The equilibrium shifts to the right.

Answer

A) The equilibrium shifts to the left.

Answer

C) The value of $K_c$ increases.

Answer

D) No shift occurs.

Question 6

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

Accepted Answer

C) $K_c$ increases.

Answer

A) $K_c$ decreases.

Answer

B) $K_c$ remains unchanged.

Answer

D) $K_c$ becomes zero.

Question 7

How does adding a catalyst affect a reversible reaction at chemical equilibrium?

Accepted Answer

A) It increases both forward and reverse rates equally without changing $K_c$.

Answer

B) It shifts equilibrium toward products.

Answer

C) It increases the value of $K_c$.

Answer

D) It lowers the reverse reaction rate.

Question 8

If the reaction quotient $Q_c$ is less than the equilibrium constant $K_c$ ($Q_c < K_c$), which way will the system shift?

Accepted Answer

B) Forward direction (to the right).

Answer

A) Reverse direction (to the left).

Answer

C) The system is already at equilibrium.

Answer

D) The reaction stops.

Question 9

According to the Arrhenius concept, an acid is a substance that:

Accepted Answer

D) Produces $	ext{H}^+$ ions in aqueous solution.

Answer

A) Accepts an electron pair.

Answer

B) Donates a proton in any solvent.

Answer

C) Produces $	ext{OH}^-$ ions in water.

Question 10

In the reaction $ ext{NH}_3(aq) + ext{H}_2 ext{O}(l) ightleftharpoons ext{NH}_4^+(aq) + ext{OH}^-(aq)$, which species is the conjugate acid of $ ext{NH}_3$?

Accepted Answer

A) $	ext{NH}_4^+$

Answer

B) $	ext{H}_2	ext{O}$

Answer

C) $	ext{OH}^-$

Answer

D) $	ext{H}^+$

Question 11

Which of the following acts as a Lewis acid?

Accepted Answer

C) $	ext{BF}_3$

Answer

A) $	ext{NH}_3$

Answer

B) $	ext{H}_2	ext{O}$

Answer

D) $	ext{Cl}^-$

Question 12

What is the ionic product of water ($K_w$) at 298 K ($25^\circ ext{C}$)?

Accepted Answer

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

Answer

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

Answer

C) $1.0 	imes 10^{-1}$

Answer

D) $1.0 	imes 10^7$

Question 13

What is the pH of a solution with a hydrogen ion concentration $[ ext{H}^+] = 1.0 imes 10^{-4}m$?

Accepted Answer

A) 4.0

Answer

B) 10.0

Answer

C) 1.0

Answer

D) 14.0

Question 14

If a solution at $25^\circ ext{C}$ has a pH of 9.0, what is its pOH?

Accepted Answer

D) 5.0

Answer

A) 9.0

Answer

B) 7.0

Answer

C) 14.0

Question 15

Which pair of compounds forms an acidic buffer solution?

Accepted Answer

C) $	ext{CH}_3	ext{COOH}$ and $	ext{CH}_3	ext{COONa}$

Answer

A) $	ext{NaOH}$ and $	ext{NaCl}$

Answer

B) $	ext{HCl}$ and $	ext{NaCl}$

Answer

D) $	ext{NH}_4	ext{OH}$ and $	ext{NH}_4	ext{Cl}$

Question 16

What is the solubility product ($K_{sp}$) expression for silver chloride: $ ext{AgCl}(s) ightleftharpoons ext{Ag}^+(aq) + ext{Cl}^-(aq)$?

Accepted Answer

A) $K_{sp} = [	ext{Ag}^+][	ext{Cl}^-]$

Answer

B) $K_{sp} = \frac{[	ext{Ag}^+][	ext{Cl}^-]}{[	ext{AgCl}]}$

Answer

C) $K_{sp} = [	ext{Ag}^+] + [	ext{Cl}^-]$

Answer

D) $K_{sp} = [	ext{Ag}^+]^2[	ext{Cl}^-]$

Question 17

What occurs to the solubility of $ ext{AgCl}$ when sodium chloride ($ ext{NaCl}$) is added to its saturated solution?

Accepted Answer

B) Solubility decreases due to the common ion effect.

Answer

A) Solubility increases.

Answer

C) Solubility remains unchanged.

Answer

D) $	ext{AgCl}$ completely decomposes.

Question 18

What is the $K_p$ expression for the decomposition: $ ext{CaCO}_3(s) ightleftharpoons ext{CaO}(s) + ext{CO}_2(g)$?

Accepted Answer

C) $K_p = P_{	ext{CO}_2}$

Answer

A) $K_p = \frac{P_{	ext{CaO}} \cdot P_{	ext{CO}_2}}{P_{	ext{CaCO}_3}}$

Answer

B) $K_p = P_{	ext{CO}_2} \cdot P_{	ext{CaO}}$

Answer

D) $K_p = \frac{1}{P_{	ext{CO}_2}}$

Question 19

For the reaction $2 ext{NO}_2(g) ightleftharpoons ext{N}_2 ext{O}_4(g)$, what happens if pressure is increased by decreasing the volume?

Accepted Answer

A) The equilibrium shifts to the right (towards $	ext{N}_2	ext{O}_4$).

Answer

B) The equilibrium shifts to the left (towards $	ext{NO}_2$).

Answer

C) There is no shift in equilibrium.

Answer

D) $K_c$ increases.

Question 20

Which aqueous solution condition represents a neutral solution at 298 K?

Accepted Answer

D) $[	ext{H}^+] = 1.0 	imes 10^{-7}m$

Answer

A) $[	ext{H}^+] = 1.0 	imes 10^{-3}m$

Answer

B) $[	ext{OH}^-] = 1.0 	imes 10^{-5}m$

Answer

C) $	ext{pH} = 5.0$

Grade 11 : Chemistry - Equilibrium (Set 2)