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JAMB Chemistry 1979 Question 7

Question 7

Chemical Equilibrium

The following reactions are stages in important industrial processes: I. N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH is negative II. 2SO2(g) + O2(g) ⇌ 2SO3(g) ΔH is negative III. N2(g) + O2(g) ⇌ 2NO(g) ΔH is positive. Which of the above forward reactions is favoured by (i) a decrease in the concentration of the pressure and (ii) an increase in temperature?

  1. A.I
  2. B.II
  3. C.III
  4. D.I and II
  5. E.I and III
Show the answer and explanation

Answer: C (III)

Explanation

Only III is endothermic, so only it is helped by a rise in temperature. It has 2 moles of gas on each side, so lowering the pressure does not work against it, whereas I and II (fewer moles on the right) are favoured by high pressure.