According to Le Chatelier’s principle, if in a reaction in equilibrium, the concentration of any reactant is increased, the equilibrium shifts in the forward reaction. On the other hand, if the concentration of any product is increased, the equilibrium shifts in the backward direction. The reverse happens if the concentrations are decreased.
For the given reaction,
2H2(g) + CO (g) ⇌CH3OH (g)
a) If the addition of H2 is taking place, it means the concentration of reactant is increasing. According to Le Chatelier’s principle, the equilibrium shifts in the forward direction.
b) If the addition of CH3OH is taking place, it means the concentration of product is increasing. According to Le Chatelier’s principle, the equilibrium shifts in the backward direction.
c) If the removal of CO is taking place, it means the concentration of reactant is decreasing, the equilibrium shifts in the backward direction. According to Le Chatelier’s principle, the equilibrium shifts in the backward direction.
d) If the removal of CH3OH is taking place, it means the concentration of product is decreasing, the equilibrium shifts in the forward direction. According to Le Chatelier’s principle, the equilibrium shifts in the forward direction.