In the manufacture of hydrogen from methane and steam, carbon monoxide is produced as an
unwanted side product. The amount of carbon monoxide is reduced by mixing the gases with
steam when the following reversible reaction takes place.
CO (g) + H2 O (g) CO2 (g) + H2 (g) ∆H negative (exothermic)
When this reaction reaches equilibrium, which of the following changes would result in more
carbon monoxide being removed?

Answer:

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.