Consider this reaction: zn(s) + 2hcl(aq) zncl2(aq) + h2(g). which change could decrease the rate of production of zncl2?

Consider this reaction: Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g). Which change could decrease the rate of production of ZnCl2?
The answer is: increasing the [HCl] 

This is supported by the "Le Chatelier's Principle" that states, "If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change."
Increasing the temperature of a system in dynamic equilibrium favours the endothermic reaction. The system counteracts the change you have made by absorbing the extra heat.Decreasing the temperature of a system in dynamic equilibrium favours the exothermic reaction. The system counteracts the change you have made by producing more heat.