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JAMB Chemistry 1992 Question 28

Question 28

Chemical Equilibrium

Which of the following equilibria shows little or no net reaction when the volume of the system is decreased?

  1. A.H2(g) + I2(g) ⇌ 2HI(g)
  2. B.2NO2(g) ⇌ N2O4(g)
  3. C.PCl5(g) ⇌ PCl3(g) + Cl2(g)
  4. D.ZnO(s) + CO2(g) ⇌ ZnCO3(s).
Show the answer and explanation

Answer: A (H2(g) + I2(g) ⇌ 2HI(g))

Explanation

Decreasing the volume raises the pressure, which favours the side with fewer gas molecules. H2 + I2 ⇌ 2HI has 2 moles of gas on each side, so it does not shift.