Mg(s) + 2hcl(aq) mc019-1.jpg h2(g) + mgcl2(aq)
what is the most likely effect of an increase in pressure on this reaction?
the reactant surface area increases.
the reaction rate decreases.
the reaction is not affected at all.
the reaction stops completely.

The increase in pressure alters the equilibrium of the reaction. In this case, the number of gaseous products in the reactant side is zero while the product side contains 1 gaseous product. The increase in pressure favors the side with less number of gaseous molecules which is the reactant side. Hence, the reaction rate decreases. 

Bar graph