Answer is: the reaction rate would decrease.
The lower is the temperature, the slower the reaction becomes.
The Haber process is procedure for the production of ammonia, in this process atmospheric nitrogen (N₂) is converted to ammonia (NH₃):
N₂ + 3H₂ ⇄ 2NH₃ ΔrH = -92 kJ/mol.
Because this is exothermic reaction (enthalpy is less than zero), at lower temperatures, the equilibrium is in favor of ammonia, but the reaction doesn't proceed at a detectable rate.
