75 free MCQs on Equilibrium, each with its own worked answer and explanation. When forward and reverse reaction rates are equal, equilibrium is reached. Learn about Kc, Kp, Le Chatelier's principle, and acid-base equilibria, including pH, buffer solutions, and solubility product.
Take the timed Equilibrium chapterwise test →75 practice questions on Equilibrium, sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Equilibrium notes.
As the reaction proceeds, reactant concentration falls and product concentration rises until both level off at equilibrium.
Q1.
The conjugate acid of ammonia (NH<sub>3</sub>) is:
Q2.
At 25 °C, the sum pH + pOH for any aqueous solution equals:
Q3.
According to Lewis, an acid is a species that:
Q4.
Chemical equilibrium is described as dynamic because:
Q5.
The equilibrium constant K<sub>c</sub> is dimensionless (has no units) when:
Q6.
Le Chatelier's principle states that when a stress is applied to a system at equilibrium, it will:
Q7.
The equilibrium constant Kc is expressed in terms of:
Q8.
At chemical equilibrium, the rate of forward reaction is:
Q9.
A very large value of Kc indicates that the reaction:
Q10.
For N₂ + 3H₂ ⇌ 2NH₃, increasing pressure will:
Q11.
At equilibrium, which statement is correct?
Q13.
A buffer solution resists changes in:
Q14.
The relationship between Kp and Kc is:
Q15.
Adding a catalyst to a system at equilibrium:
Q16.
A reversible reaction reaches equilibrium when the forward and backward reaction rates become:
Q17.
At equilibrium, the measurable concentrations of reactants and products:
Q18.
The equilibrium constant written in terms of molar concentrations is denoted:
Q19.
For aA + bB ⇌ cC + dD, the expression Kc = [C]ᶜ[D]ᵈ divided by:
Q20.
A catalyst added to a system at equilibrium:
Q21.
The ionic product of water, Kw, at 25 °C is:
Q22.
A solution having a pH less than 7 at 25 °C is:
Q24.
According to Arrhenius, an acid releases which ion in aqueous solution?
Q25.
Le Chatelier’s principle predicts how an equilibrium responds to a change in concentration, pressure or:
Q26.
For A ⇄ B, K<sub>c</sub> = 4. Starting from 1 M A and no B, the equilibrium concentration of B is:
Q27.
For 2SO<sub>3</sub>(g) ⇌ 2SO<sub>2</sub>(g) + O<sub>2</sub>(g), the relation between K<sub>p</sub> and K<sub>c</sub> (Δn = +1) is:
Q28.
One mole each of H<sub>2</sub> and I<sub>2</sub> are placed in a 1 L flask; at equilibrium 0.8 mol of each has reacted. K<sub>c</sub> for H<sub>2</sub> + I<sub>2</sub> ⇌ 2HI is:
Q29.
The pH of a 0.005 M H<sub>2</sub>SO<sub>4</sub> solution (assume complete dissociation) is:
Q30.
A buffer contains 0.2 M CH<sub>3</sub>COOH and 0.2 M CH<sub>3</sub>COONa (pK<sub>a</sub> = 4.74). Its pH is:
Q31.
For PCl₅(g) ⇌ PCl₃(g) + Cl₂(g), increasing pressure will:
Q32.
For N₂ + 3H₂ ⇌ 2NH₃, the relationship between Kp and Kc is:
Q33.
For weak acid HA with Ka = 1.8 × 10⁻⁵, pH of 0.1 M solution is approximately:
Q34.
The Henderson-Hasselbalch equation (pH = pKa + log[A⁻]/[HA]) is used to calculate:
Q35.
The common ion effect causes solubility of a sparingly soluble salt to:
Q36.
For AgCl with Ksp = 1.8 × 10⁻¹⁰, its molar solubility is:
Q37.
For an exothermic reaction, increasing temperature will:
Q38.
Which of the following increases Kc for an endothermic reaction?
Q39.
For the reaction 2SO<sub>2</sub>(g) + O<sub>2</sub>(g) <=> 2SO<sub>3</sub>(g), how does adding an inert gas at constant volume affect the equilibrium?
Q40.
A buffer solution is prepared by mixing a weak acid with its conjugate base. Why does this mixture resist large changes in pH when a small amount of acid or base is added?
Q42.
Increasing the total pressure on the equilibrium N₂ + 3H₂ ⇌ 2NH₃ shifts it:
Q43.
For a gaseous reaction in which Δn = 0, the value of Kp is:
Q44.
When the reaction quotient Q is smaller than the equilibrium constant K, the reaction proceeds:
Q45.
Adding a common ion to a solution of a weak acid decreases its:
Q46.
A buffer solution is one that resists changes in:
Q48.
According to the Brønsted–Lowry theory, a base is a species that:
Q49.
For the exothermic equilibrium 2SO₂ + O₂ ⇌ 2SO₃, raising the temperature shifts it:
Q51.
A weak acid is 1% dissociated (alpha = 0.01) in a 0.1 M solution. Its dissociation constant K<sub>a</sub> is about:
Q52.
A buffer is made from 0.1 mol CH<sub>3</sub>COOH and 0.05 mol CH<sub>3</sub>COO<sup>−</sup> (pK<sub>a</sub> = 4.74). Its pH is about:
Q53.
If K<sub>c</sub> for N<sub>2</sub> + 3H<sub>2</sub> ⇌ 2NH<sub>3</sub> equals K, then K<sub>c</sub> for NH<sub>3</sub> ⇌ ½N<sub>2</sub> + 3/2 H<sub>2</sub> is:
Q54.
Equal volumes of 2 × 10<sup>−3</sup> M BaCl<sub>2</sub> and 2 × 10<sup>−3</sup> M Na<sub>2</sub>SO<sub>4</sub> are mixed. Given K<sub>sp</sub>(BaSO<sub>4</sub>) = 1 × 10<sup>−10</sup>, will BaSO<sub>4</sub> precipitate?
Q55.
Assertion (A): For an endothermic reaction, K<sub>c</sub> increases as temperature rises. Reason (R): Raising the temperature favours the forward (heat-absorbing) direction.
Q56.
For H₂ + I₂ ⇌ 2HI, Kc = 45.9 at 490°C. If [H₂] = [I₂] = 0.1 M at equilibrium, [HI] is:
Q58.
For PCl₅ ⇌ PCl₃ + Cl₂ at pressure P with small degree of dissociation α, Kp is approximately:
Q59.
Ksp of Ag₂CrO₄ = 1.12 × 10⁻¹². Its molar solubility is:
Q60.
Which salt hydrolyses to give an alkaline solution?
Q61.
The ionic product of water Kw increases with temperature because:
Q62.
AgCl (Ksp = 10⁻¹⁰) and AgBr (Ksp = 10⁻¹³) are both dissolved. When Ag⁺ is slowly added, which precipitates first?
Q63.
For an exothermic reaction with Kc = 0.04 at 1000 K, as temperature increases Kc will:
Q64.
A 0.1 M solution of a weak base BOH has a degree of dissociation of 0.02. What is the value of Kb for this base?
Q65.
For the equilibrium N<sub>2</sub>O<sub>4</sub>(g) <=> 2NO<sub>2</sub>(g), the total pressure at equilibrium is P and the degree of dissociation of N<sub>2</sub>O<sub>4</sub> is alpha. Which expression correctly gives Kp in terms of alpha and P?
Q66.
For a sparingly soluble salt AB with molar solubility S, its solubility product is:
Q67.
By Ostwald’s dilution law for a weak acid, Ka in terms of concentration C and degree of dissociation α is:
Q68.
In the Henderson–Hasselbalch equation, the pH of an acidic buffer is pH = pKa +:
Q69.
The degree of hydrolysis of the salt of a weak acid and a strong base increases on:
Q70.
If the Ka of acetic acid is 1.8 × 10⁻⁵, its pKa is approximately:
Q71.
A large equilibrium constant (K ≫ 1) indicates that at equilibrium:
Q73.
Adding an inert gas to a gaseous equilibrium at constant volume:
Q74.
Given ΔG° = −2.303 RT log K, a positive value of ΔG° means the equilibrium constant K is:
Q75.
A salt formed from a strong acid and a weak base, when dissolved in water, gives a solution that is:
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