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Chemical equilibria, Le Chatelier’s principle and Kc​

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Question 14
a.

1.50 mol of a diester with molecular formula C6H10O4\text{C}_6\text{H}_{10}\text{O}_4C6​H10​O4​ is added to 2.00 mol of water in the presence of an acid catalyst. The mixture is allowed to reach equilibrium at a constant temperature:

C6H10O4(l)+2H2O(l)⇌2CH3COOH(l)+HO(CH2)2OH(l) \text{C}_6\text{H}_{10}\text{O}_4(\text{l}) + 2\text{H}_2\text{O}(\text{l}) \rightleftharpoons 2\text{CH}_3\text{COOH}(\text{l}) + \text{HO}(\text{CH}_2)_2\text{OH}(\text{l}) C6​H10​O4​(l)+2H2​O(l)⇌2CH3​COOH(l)+HO(CH2​)2​OH(l)

At equilibrium, x molx\text{ mol}x mol of ethanoic acid are present in the mixture. Complete the details of the equilibrium mixture by finding the equilibrium amounts, in terms of xxx, of:

  • Diester
  • Water
  • Diol
[3]
b.

Deduce the structure of the diester C6H10O4\text{C}_6\text{H}_{10}\text{O}_4C6​H10​O4​ used in this reaction.

[1]
c.

A new equilibrium mixture of the same substances is prepared at a different temperature.

C6H10O4(l)+2H2O(l)⇌2CH3COOH(l)+HO(CH2)2OH(l) \text{C}_6\text{H}_{10}\text{O}_4(\text{l}) + 2\text{H}_2\text{O}(\text{l}) \rightleftharpoons 2\text{CH}_3\text{COOH}(\text{l}) + \text{HO}(\text{CH}_2)_2\text{OH}(\text{l}) C6​H10​O4​(l)+2H2​O(l)⇌2CH3​COOH(l)+HO(CH2​)2​OH(l)

At equilibrium, this mixture contains:

  • 0.600 mol of diester
  • 0.480 mol of ethanoic acid
  • 0.150 mol of diol

The value of the equilibrium constant, KcK_cKc​, is 0.360 at this temperature. Calculate the amount of water, in mol, in this new equilibrium mixture.

[3]
Markscheme

Chemical equilibria, Le Chatelier’s principle and Kc Questions

  1. A Level
  2. /Chemistry
  3. /Chemical equilibria, Le Chatelier’s principle and Kc

24 exam-style questions on AQA A Level Chemistry Chemical equilibria, Le Chatelier’s principle and $K_c$, covering Chemical equilibria and Le Chatelier's principle and Equilibrium constant $K_c$ for homogeneous systems. Each one has a worked solution and a mark scheme showing where the marks go.

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