A graph of concentration against time for N2(g) + 3H2(g) ⇌ 2NH3(g), at constant temperature and volume, shows three flat lines until time t₁. At t₁ the H2 line jumps up sharply and then falls gradually, the N2 line falls gradually and the NH3 line rises gradually, until all three level off at new values. What was done at t₁?
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A sudden rise in [H2] alone means H2 was added. By Le Chatelier's principle the system uses up some of it by reacting with N2, so [N2] falls and [NH3] rises until a new equilibrium is set up.
- B.
Removing NH3 would make the NH3 line drop sharply at t₁; instead it rises gradually.
- C.
A catalyst does not change the equilibrium concentrations, so all lines would stay flat.
- D.
Doubling the volume would lower every concentration sharply at t₁, and the volume is stated to be constant.
NCERT: Class 11 Chemistry, Chapter 6