Class 11 – Chemical Equilibrium (40 MCQs)
Basic Concepts of Equilibrium (1–5)
- A reaction is said to be in equilibrium when:
a) Forward reaction stops
b) Reverse reaction stops
c) Rate of forward reaction = Rate of reverse reaction
d) Concentrations of reactants are zero - Dynamic equilibrium implies:
a) No reaction occurs
b) Forward and backward reactions occur at same rate
c) Concentrations of products increase
d) Temperature drops - For the reaction N₂ + 3H₂ ⇌ 2NH₃, at equilibrium:
a) Only reactants are present
b) Only products are present
c) Both forward and reverse reactions continue
d) Forward reaction stops - Equilibrium can be achieved in:
a) Only gases
b) Only liquids
c) Both gases and liquids
d) Only solids - Reversible reactions are:
a) Only exothermic
b) Only endothermic
c) Reactions that can proceed forward and backward
d) Irreversible
Law of Mass Action & Equilibrium Constant (6–12)
- For the reaction aA + bB ⇌ cC + dD, the equilibrium constant Kc is:
a) [A]^a[B]^b / [C]^c[D]^d
b) [C]^c[D]^d / [A]^a[B]^b
c) [C][D]/[A][B]
d) [A][B]/[C][D] - Kp is related to Kc by:
a) Kp = Kc(RT)^Δn
b) Kp = Kc/(RT)^Δn
c) Kp = Kc + RT
d) Kp = Kc – RT - Δn in Kp formula represents:
a) Total moles of reactants
b) Total moles of products
c) Moles of products – moles of reactants (gaseous)
d) Moles of reactants – moles of products (solid/liquid) - For a heterogeneous equilibrium, the equilibrium expression:
a) Includes all reactants and products
b) Excludes solids and pure liquids
c) Includes solids only
d) Includes liquids only - Kc is:
a) Dimensionless
b) Always 1
c) Depends on temperature
d) Independent of temperature - For 2SO₂ + O₂ ⇌ 2SO₃, Kc expression is:
a) [SO₂]²[O₂] / [SO₃]²
b) [SO₃]² / ([SO₂]²[O₂])
c) [SO₃]/[SO₂][O₂]
d) [SO₂][O₂]/[SO₃] - Kc = 1 means:
a) Reaction favors reactants
b) Reaction favors products
c) Neither reactants nor products favored
d) Reaction stops
Homogeneous & Heterogeneous Equilibria (13–17)
- Heterogeneous equilibrium involves:
a) Only gases
b) Only liquids
c) More than one phase
d) Only solids - In N₂(g) + 3H₂(g) ⇌ 2NH₃(g), homogeneous equilibrium:
a) Gaseous reactants and products
b) Solid reactants only
c) Liquid reactants only
d) Mixed phase - Solids and pure liquids are:
a) Included in Kc expression
b) Excluded from Kc expression
c) Only partially included
d) Dependent on temperature - For a reaction in aqueous solution, homogeneous equilibrium exists if:
a) All reactants are solids
b) All reactants and products are dissolved
c) Some reactants are gases
d) Some reactants are liquids - Equilibrium constant for heterogeneous reactions is:
a) Independent of amount of solids/pure liquids
b) Dependent on amount of solids
c) Always 1
d) Temperature-independent
Le Chatelier’s Principle (18–24)
- According to Le Chatelier’s principle, if concentration of reactants increases:
a) No effect
b) Equilibrium shifts to products
c) Equilibrium shifts to reactants
d) Reaction stops - Increasing pressure on 2SO₂ + O₂ ⇌ 2SO₃:
a) Shifts equilibrium to left
b) Shifts equilibrium to right
c) No change
d) Reaction stops - Temperature increase in exothermic reaction:
a) Shifts equilibrium forward
b) Shifts equilibrium backward
c) No change
d) Reaction accelerates only - Temperature increase in endothermic reaction:
a) Shifts forward
b) Shifts backward
c) Stops reaction
d) No effect - Addition of inert gas at constant volume:
a) Shifts equilibrium
b) No effect
c) Stops reaction
d) Changes Kc - Removal of products:
a) Equilibrium shifts to reactants
b) Equilibrium shifts to products
c) No change
d) Decreases Kc - For N₂O₄ ⇌ 2NO₂, increase in pressure:
a) Shifts forward
b) Shifts backward
c) Shifts to side with fewer moles
d) No effect
Factors Affecting Equilibrium (25–30)
- Increasing concentration of a reactant:
a) No effect
b) Shifts equilibrium toward products
c) Shifts equilibrium toward reactants
d) Stops reaction - Decreasing temperature in exothermic reaction:
a) Shifts equilibrium forward
b) Shifts equilibrium backward
c) Stops reaction
d) No change - Increasing volume (decreasing pressure) for 2A + B ⇌ 3C:
a) Shifts equilibrium to reactants
b) Shifts equilibrium to products
c) No effect
d) Kc changes - Catalysts:
a) Change equilibrium constant
b) Speed up forward and backward reactions equally
c) Shift equilibrium
d) Stop reaction - Kp increases with:
a) Temperature increase in endothermic reactions
b) Temperature decrease in endothermic reactions
c) Pressure increase
d) Catalyst addition - For 2NO₂ ⇌ N₂O₄ (exothermic), adding heat:
a) Shifts forward
b) Shifts backward
c) No effect
d) Stops reaction
Ionic Equilibrium & Solubility Product (31–36)
- Solubility product (Ksp) applies to:
a) Gaseous equilibrium
b) Saturated solution of sparingly soluble salts
c) All reactions
d) Reversible reactions only - For AgCl(s) ⇌ Ag⁺ + Cl⁻, Ksp =
a) [Ag⁺][Cl⁻]
b) [Ag⁺]/[Cl⁻]
c) [Ag⁺]²[Cl⁻]²
d) [Ag⁺]+[Cl⁻] - Higher Ksp →
a) Less soluble
b) More soluble
c) Insoluble
d) Constant solubility - Common ion effect:
a) Increases solubility
b) Decreases solubility
c) No effect
d) Makes salts more ionic - Ksp is temperature dependent:
a) Yes
b) No
c) Only for solids
d) Only for liquids - Solubility of AgCl decreases in presence of NaCl due to:
a) Temperature change
b) Common ion effect
c) Pressure effect
d) Catalyst
Miscellaneous NEET Conceptual Questions (37–40)
- If Kc >> 1, reaction favors:
a) Reactants
b) Products
c) Neither
d) Depends on temperature - If Kc << 1, reaction favors:
a) Products
b) Reactants
c) Both equally
d) None - Dynamic equilibrium occurs when:
a) Only forward reaction occurs
b) Only backward reaction occurs
c) Forward and backward reactions occur at equal rates
d) Reaction stops - At equilibrium, ΔG =
a) Positive
b) Negative
c) Zero
d) Infinite
Answer Key – Class 11 Chemistry: Chemical Equilibrium (40 MCQs)
Basic Concepts of Equilibrium (1–5)
- c) Rate of forward reaction = Rate of reverse reaction – Equilibrium occurs when reaction rates are equal.
- b) Forward and backward reactions occur at same rate – Definition of dynamic equilibrium.
- c) Both forward and reverse reactions continue – At equilibrium, reaction doesn’t stop; net change = 0.
- c) Both gases and liquids – Equilibrium can occur in any phase.
- c) Reactions that can proceed forward and backward – Reversible reactions.
Law of Mass Action & Equilibrium Constant (6–12)
- b) [C]^c[D]^d / [A]^a[B]^b – Standard expression for Kc.
- a) Kp = Kc(RT)^Δn – Relates Kp and Kc for gaseous reactions.
- c) Moles of products – moles of reactants (gaseous) – Definition of Δn.
- b) Excludes solids and pure liquids – Concentrations of pure solids/liquids not included.
- c) Depends on temperature – Kc is temperature-dependent.
- b) [SO₃]² / ([SO₂]²[O₂]) – Expression for Kc.
- c) Neither reactants nor products favored – Kc ≈ 1 indicates balance.
Homogeneous & Heterogeneous Equilibria (13–17)
- c) More than one phase – Heterogeneous equilibrium involves solids, liquids, or gases in different phases.
- a) Gaseous reactants and products – Homogeneous equilibrium in same phase.
- b) Excluded from Kc expression – Solids/pure liquids omitted.
- b) All reactants and products are dissolved – Homogeneous aqueous equilibrium.
- a) Independent of amount of solids/pure liquids – Only concentrations of species in solution/gas considered.
Le Chatelier’s Principle (18–24)
- b) Equilibrium shifts to products – System compensates for added reactant.
- c) No change – Pressure change affects side with different moles; here 2+1 ⇌2 → moles same → no shift.
- b) Shifts equilibrium backward – Exothermic reaction, increasing temperature favors reverse reaction.
- a) Shifts forward – Endothermic, heating favors forward reaction.
- b) No effect – Inert gas at constant volume does not change partial pressures.
- b) Equilibrium shifts to products – Removing products shifts equilibrium to produce more.
- c) Shifts to side with fewer moles – Increased pressure favors side with fewer gas moles.
Factors Affecting Equilibrium (25–30)
- b) Shifts equilibrium toward products – Adding reactant shifts forward.
- a) Shifts equilibrium forward – Exothermic, decreasing temperature favors forward reaction.
- a) Shifts equilibrium to reactants – Increasing volume (decreasing pressure) favors side with more moles; 2+1 ⇌3 → 3 moles → shift forward? Actually 2+1 →3 → increasing volume favors side with more moles → products. Correction: b) Shifts equilibrium to products.
- b) Speed up forward and backward reactions equally – Catalysts do not shift equilibrium.
- a) Temperature increase in endothermic reactions – K increases for endothermic with heat addition.
- b) Shifts backward – Exothermic, adding heat shifts equilibrium backward.
Ionic Equilibrium & Solubility Product (31–36)
- b) Saturated solution of sparingly soluble salts – Ksp applies here.
- a) [Ag⁺][Cl⁻] – Definition of solubility product.
- b) More soluble – Higher Ksp → greater solubility.
- b) Decreases solubility – Common ion effect suppresses solubility.
- a) Yes – Ksp depends on temperature.
- b) Common ion effect – Adding NaCl reduces AgCl solubility due to Cl⁻.
Miscellaneous NEET Conceptual Questions (37–40)
- b) Products – Kc >> 1 → favors products.
- b) Reactants – Kc << 1 → favors reactants.
- c) Forward and backward reactions occur at equal rates – Definition of dynamic equilibrium.
- c) Zero – Gibbs free energy change ΔG = 0 at equilibrium.
Disclaimer:
All MCQs on this page are , created for educational purposes only. They are intended for practice and NEET/Class 11 Chemistry preparation and do not guarantee any specific exam results.