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Chemical Equilibrium MCQs for MDCAT Practice

Chemistry section, Chemical Equilibrium chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

The bank has 994 active questions on this chapter. Your first 500 practice attempts are free, and every attempt includes a worked explanation.

  1. Question 1
    1 mole of CH3COOH and 1 mole of C2H5OH react to produce 2/3 mole of CH3COOC2H5. The equilibrium constant is
    • 2
    • -4
    • 8
    • +4 (correct answer)
    Correct answer: D
    Calculate the equilibrium constant (Kc) for esterification using initial moles and product formed, demonstrating the application of the equilibrium expression.
  2. Question 2
    In the Haber process for manufacturing of ammonia, Nitrogen is taken from:
    • Proteins occurring in living bodies
    • Ammonium salts obtained industrially
    • Air (correct answer)
    • Minerals containing nitrates
    Correct answer: C
    The Haber process, crucial for ammonia synthesis, utilizes nitrogen sourced directly from the Earth's abundant atmosphere.
  3. Question 3
    Which one of the following statements is correct about a reaction for which the equilibrium constant is independent of temperature?
    • The activation energies for both forward and reverse reactions are zero
    • The enthalpy change is zero (correct answer)
    • Its rate constants do not vary with temperature
    • There are an equal number of moles of reactants and products in it
    Correct answer: B
    A reaction's equilibrium constant (K) is temperature-independent only when its enthalpy change (ΔH) is zero, indicating no net heat exchange.
  4. Question 4
    Which of the following is an example of an acidic buffer solution?
    • 0.1 M NaOH + 0.1 M NaCl
    • 0.1 M NaOH + 0.1 M HCl
    • 0.1 M NH3 + 0.1 M NH4Cl
    • 0.1 M NaCl + 0.1 M HNO3 (correct answer)
    Correct answer: D
    An acidic buffer resists pH change by containing a weak acid and its conjugate base, or a weak base and its conjugate acid. Option D fits this definition.
  5. Question 5
    A + B ⇋ C + D. If at equilibrium A = 0.4 mole/dm3, B = 0.5 mole/dm3, C = 0.3 mole/dm3 and D = 0.8 mole/dm3. Calculate Kc for the reaction 2A + B ⇋ C + D.
    • 3 (correct answer)
    • 1.5
    • 2
    • None of the above
    Correct answer: A
    This question tests the calculation of Kc for a modified reaction based on equilibrium concentrations of the original reaction, emphasizing proper stoichiometry in the Kc expression.
  6. Question 6
    Consider the reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g) + heat. If the temperature is decreased, which way will the equilibrium shift?
    • Towards the reactants
    • towards the products (correct answer)
    • no shift will occur
    • it depends on the initial concentrations of the reactants and products
    Correct answer: B
    Decreasing temperature shifts exothermic reactions towards products, as dictated by Le Chatelier's Principle.
  7. Question 7
    Suppose the following system has reached equilibrium at a certain temperature: N2​O4​(g)→2NO2​(g) Adding N2​O4​ to the system will:
    • Start forward reaction (correct answer)
    • Start reverse reaction
    • Not disturb equilibrium
    • Raise the temperature of system
    Correct answer: A
    Adding a reactant shifts equilibrium according to Le Chatelier's principle. Increasing N2​O4​ drives the reaction forward to consume the added reactant.
  8. Question 8
    A small value of Kc suggest that position of equilibrium
    • Is constantly changing
    • Lies towards left (correct answer)
    • Remains same after adding reactant
    • Independent of T
    Correct answer: B
    A small Kc value indicates that the equilibrium predominantly favors reactants, meaning the equilibrium lies to the left, with minimal product formation.

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