Consider the reaction between hydrogen gas and chlorine gas to form hydrogen chloride gas in a closed cylinder with a movable piston.

H2(g) + Cl2(g) → 2 HCl(g)

Predict what would happen to the reaction rate for a mixture containing both reactants if the following occur.

(a) The pressure on the reaction mixture is increased at constant temperature (while keeping the reaction components in the gaseous phase).

the rate increases the rate decreases the rate does not change

(b) The temperature is reduced so that chlorine is converted to the liquid state.

the rate increases the rate decreases the rate does not change

(c) A catalyst is added to the reaction mixture.

the rate increases the rate decreases the rate does not change