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JAMB Chemistry 1979 Question 32

Question 32

Chemical Equilibrium

The reaction between hydrogen and iodine may be represented by the equation H2(g) + I2(g) ⇌ 2HI(g), and is exothermic. Therefore

  1. A.an increase in temperature favours the forward reaction
  2. B.an increase in pressure favours the backward reaction
  3. C.both pressure and temperature must be increased to favour the forward reaction
  4. D.a decrease in temperature will favour the forward reaction
  5. E.a decrease in pressure and an increase in temperature will favour the forward reaction.
Show the answer and explanation

Answer: D (a decrease in temperature will favour the forward reaction)

Explanation

For an exothermic forward reaction, lowering the temperature shifts the equilibrium to the right. Pressure has no effect because there are 2 moles of gas on each side.