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Chemical equilibria, Le Chatelier’s principle and $K_c$

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Question 5

This question is about an equilibrium.

A(aq)+2B(aq)⇌C(aq)+3D(aq) \text{A(aq)} + 2\text{B(aq)} \rightleftharpoons \text{C(aq)} + 3\text{D(aq)} A(aq)+2B(aq)⇌C(aq)+3D(aq)

A 30.0 cm330.0\text{ cm}^330.0 cm3 sample of a solution of A\text{A}A is added to a 20.0 cm320.0\text{ cm}^320.0 cm3 sample of a solution of B\text{B}B. The mixture is allowed to reach equilibrium.

The amounts in the equilibrium mixture are:

  • A=0.0150 mol\text{A} = 0.0150\text{ mol}A=0.0150 mol
  • B=0.0250 mol\text{B} = 0.0250\text{ mol}B=0.0250 mol
  • C=0.0120 mol\text{C} = 0.0120\text{ mol}C=0.0120 mol
  • D=0.0360 mol\text{D} = 0.0360\text{ mol}D=0.0360 mol
1.

Calculate the amount, in moles, of B\text{B}B before the reaction with A\text{A}A. Use your answer to calculate the concentration, in mol dm−3\text{mol dm}^{-3}mol dm−3, of B\text{B}B in the initial 20.0 cm320.0\text{ cm}^320.0 cm3 sample.

[4]
2.

Give the expression for the equilibrium constant, KcK_{\text{c}}Kc​. Calculate the value of KcK_{\text{c}}Kc​ and deduce its units.

[5]
3.

Explain why the amount of D\text{D}D increases when water is added to the equilibrium mixture.

[3]

Chemical equilibria, Le Chatelier’s principle and $K_c$ Questions

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