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2 marksPrinciples of Chemical Equilibrium

CAPE Chemistry Unit 1 · May/June 2023 · Paper 2 · Question 2(a)(vi)

A student warmed frozen N₂O₄ in a sealed tube, decomposing it to brown NO₂ gas until reaching dynamic equilibrium according to N₂O₄(g) ⇌ 2 NO₂(g), ΔH = +58.0 kJ mol⁻¹.

Account for the shape of the graph drawn in (a)(v).

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Other parts of this question

  1. 2(a)(i)Explain the term 'dynamic equilibrium'.[2 marks]
  2. 2(a)(ii)State what is observed when dynamic equilibrium is reached in the reaction above.[1 mark]
  3. 2(a)(iii)State Le Chatelier's Principle.[1 mark]
  4. 2(a)(iv)Write the expression for K_p for the reaction above.[1 mark]
  5. 2(a)(v)In the space provided, draw a graph to show how the concentrations of N₂O₄(g) and NO₂(g) are expected to change as the reaction proceeds towards equilibrium.[2 marks]
  6. 2(a)(vii)State what is observed when the sealed tube is cooled to 0 °C. Outline the reason for what is observed.[2 marks]
  7. 2(b)(i)State the difference in behaviour between a strong acid and a strong base according to the Brønsted-Lowry Theory.[2 marks]
  8. 2(b)(ii)Write the reaction for the dissociation of CH₃COOH.[1 mark]
  9. 2(b)(iii)Complete Table 2, using the variable x to generate expressions for the equilibrium concentrations of the reaction components for a 0.30 M solution of CH₃COOH.[6 marks]
  10. 2(b)(iv)Generate an expression for K_a for this reaction using equilibrium expressions obtained in (b)(iii).[1 mark]
  11. 2(b)(v)Calculate the pH of a 0.30 M solution of CH₃COOH at 25 °C, if x is 0.0023 M.[3 marks]
  12. 2(c)(i)Figure 1 is a diagram of a voltaic cell. Give the correct labels that correspond to the letters A, B and C on the voltaic cell.[3 marks]
  13. 2(c)(ii)Describe an observation expected during electrolysis.[1 mark]
  14. 2(c)(iii)Describe an observed change if the cell components are based on the cell type Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s).[1 mark]
  15. 2(c)(iv)State a chemical compound which is in the salt bridge.[1 mark]

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