Free Chemical Equilibrium MCQs with Answers
625 Chemical Equilibrium MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Reversible reactions reach dynamic equilibrium when forward and reverse rates become equal, and Le Chatelier's principle predicts the effect of changing concentration, pressure or temperature. The chapter also covers solubility product, the common ion effect, buffer action and the conditions used in Haber's process, with equilibrium shifts distinguished from changes in the equilibrium constant.
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625 questions · page 5 of 32
- A. H2S2O7
- B. HSO4-
- C. SO3
- D. S
Explanation: In the contact process, SO₃ is not added directly to water because it forms a mist that is hard to absorb.
Correct answer: H2S2O7- A. Temperature
- B. Pressure
- C. Catalyst
- D. Initial concentrations
Explanation: Changing the temperature shifts the equilibrium position based on whether the reaction is endothermic (absorbs heat) or exothermic…
Correct answer: Temperature- A. The Amount of product formed
- B. Product of the molar concentration of the reactant
- C. The initial concentration of reactant
- D. Catalyst
Explanation: The law of mass action states that reaction rate depends on how frequently reactant molecules collide.
Correct answer: Product of the molar concentration of the reactant- A. ½ N2(g) + ½ O2 (g) ⇌ NO(g)
- B. PCl5(g) ⇌ PCl3(g) + Cl2(g)
- C. 2NO2 (g) ⇌ N2O4(g)
- D. SO2Cl2(g) ⇌ SO2(g) + Cl2(g)
Explanation: Pressure affects only reactions where the number of gas moles changes. In option A, reactants have 1 mole of gas total (0.5 + 0.5), and…
Correct answer: ½ N2(g) + ½ O2 (g) ⇌ NO(g)85. If the initial ratio of products to reactants(the reaction quotient) is greater than the Kc then:
- A. The reaction will shift towards the reverse direction.
- B. More quantity of products is obtained.
- C. The ratio increases to the value of Kc.
- D. Equilibrium has been attained.
- E. There is no shifting of reaction.
Explanation: If the reaction quotient Q > Kc , there are too many products compared to equilibrium.
Correct answer: The reaction will shift towards the reverse direction.- A. Decreases three times
- B. Decreases nine times
- C. Increases six times
- D. Increases nine times
Explanation: By the law of mass action, the rate ∝ (active mass of A)² × (active mass of B).
Correct answer: Increases nine times- A. Rate constant
- B. Rate of reaction
- C. Rate equation
- D. Rate law
- E. Both A & D
Explanation: The rate of reaction measures how fast reactants are consumed or products are formed.
Correct answer: Rate of reaction- A. The values of K, and Kc are different
- B. The value of K, is greater than K.
- C. The value of K, is greater than Kp
- D. The values of K, and Kc are the same
Explanation: For gaseous reactions, K and K are related by𝐾𝑝 = 𝐾𝑐 (𝑅𝑇) Δ𝑛 , whereΔn is the change in moles of gas.
Correct answer: The values of K, and Kc are the same- A. No unit
- B. mol?-dm-t
- C. mol·dm⁻³
- D. mol·dm³
Explanation: The equilibrium expression is K = [NO₂]² / [N₂O₄]. The units are (mol·dm⁻³)² / (mol·dm⁻³) = mol·dm⁻³
Correct answer: mol·dm⁻³- A. As solubility product decreases
- B. As solubility becomes unsaturated
- C. Due to the common ion effect of Cl
- D. As solution becomes supersaturated
Explanation: In the case of the common ion effect, the presence of a common ion (Cl ) in the solution decreases the solubility or ionization of the…
Correct answer: Due to the common ion effect of Cl- A. Law of mass action
- B. Hess's law
- C. Common ion effect
- D. Henry's law
Explanation: Adding HCl introduces extra Cl⁻ ions into the saturated NaCl solution. This suppresses the dissociation of NaCl, reducing its solubility.
Correct answer: Common ion effect- A. It helps to predict the direction of the reaction.
- B. It tells about the extent of the reaction.
- C. It tells about the rate of reaction.
- D. None of these.
Explanation: The equilibrium constant (Kc ) provides information about the position of equilibrium (direction and extent) but gives no information…
Correct answer: It tells about the rate of reaction.- A. The reaction proceeds in the forward direction at 300 K
- B. At 1200 K, the reaction proceeds in the reverse direction
- C. At 1200 K, Kₚ > 1
- D. At 300 K, the products will be favored more than reactants at equilibrium
Explanation: By calculating the Gibbs Free Energy (ΔG° = ΔH° - TΔS°), the reaction is found to be non-spontaneous in the forward direction at 1200 K…
Correct answer: At 1200 K, Kₚ > 1- A. Constant
- B. Different
- C. Maximum
- D. Equal
Explanation: Chemical equilibrium is a dynamic state where the rate of the forward reaction equals the rate of the reverse reaction.
Correct answer: Constant- A. Both forward and reverse reactions do not occur simultaneously
- B. Both forward and reverse reactions occur simultaneously but under different conditions
- C. Both forward and reverse reactions occur simultaneously under the same conditions
- D. Forward and reverse reactions take place at different times and different conditions
Explanation: A key feature of dynamic equilibrium is that the forward and reverse reactions are occurring continuously and simultaneously at the same…
Correct answer: Both forward and reverse reactions occur simultaneously under the same conditions- A. (concentration)⁺²
- B. (concentration)⁺¹
- C. (concentration)⁻¹
- D. No units
Explanation: The units for K are determined by (concentration) , where Δn is the change in moles of gas (products - reactants).
Correct answer: (concentration)⁺¹- A. 1
- B. 0.25
- C. 0.5
- D. 0.625
Explanation: If 1 mole of HI is 50% dissociated, at equilibrium we have 0.5 mol HI, 0.25 mol H₂, and 0.25 mol I₂.
Correct answer: 0.25- A. Ke = 10-30
- B. Ke = 1030
- C. Ke= 1
- D. Ke= 0
Explanation: If the Ke value is very high, the reaction is more favourable in the forward direction. Hence, option b is correct.
Correct answer: Ke = 1030- A. 1
- B. 2
- C. 3
- D. 4
Explanation: The reaction proceeds as follows:CH 3COOH +C2 H5OH ⇌ CH3COOC2H5 + H2OThe Kc calculation is shown in the image below:
Correct answer: 4- A. 0.2
- B. 2
- C. 4
- D. 8
Explanation: The calculation below proves that the value of Kc is 2.
Correct answer: 2