Which factor would only affect the rate of the third reaction?

Question

N₂(g) + O₂(g) → 2NO(g)

O(g) +1/2 O₂(g) → CO₂(g)

Na(s) + HCl(l) → NaCl(aq) +1/2 H₂(g)

Which factor would only affect the rate of the third reaction?

Answer 1

The second reaction doesn't seem possible. You have oxygen as reactants and carbon dioxide as a product. Where does the carbon atom come from? If this is supposed to be C(s) + O2(g) ==> CO2(g), then a factor that would only affect the third reaction would be pressure.

Pressure would only affect reaction 3 because there is a gas on the product side and no gas on the reactant side. According to Le Chatelier's Principle, a change in pressure would affect the equilibrium of this reaction.