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MCQ practice · SSC Chemistry Board questions · Chapter 7: Chemical Reactions

Dhaka Board 2023

Which has an effect of pressure?

Think it through first, then pick an option.

  1. a NH₄CNO →(Δ) H₂N-CO-NH₂
  2. b N₂(g) + O₂(g) ⇌ 2NO(g)
  3. c 3NO₂(g) + H₂O(g) ⇌ 2HNO₃(g) + NO(g)
  4. d H₂(g) + Cl₂(g) ⇌ 2HCl(g)
Answer and explanation

Correct answer: c 3NO₂(g) + H₂O(g) ⇌ 2HNO₃(g) + NO(g)

4 moles left, 3 right; the moles change, so there is an effect.

Why the other options are wrong

  • a NH₄CNO →(Δ) H₂N-CO-NH₂: This is isomerization, not a reversible gas equilibrium.
  • b N₂(g) + O₂(g) ⇌ 2NO(g): Both sides hold 2 moles of gas, so pressure has no effect.
  • d H₂(g) + Cl₂(g) ⇌ 2HCl(g): Both sides hold 2 moles of gas, so pressure has no effect.