14) D
A – Wrong
The addition of a catalyst never affects the equilibrium of a reaction.
B – Wrong
Number of moles of gas on left side = Number of moles of gas on right side. Hence, decreasing pressure will produce no change.
C – Wrong
Number of moles of gas on left side = Number of moles of gas on right side. Hence, decreasing pressure will produce no change.
D – Correct
Decreasing temperature will favour the exothermic reaction (forward reaction which reduces amount of CO)
E – Wrong
No nitrogen is involved so it would have no effect on this reaction.