Examine the chemical equation and statement. Mg+2HCl⇌MgCl2+H2
The reaction is at equilibrium. The forward reaction is endothermic, and the reverse reaction is exothermic.
Given a decrease in temperature, how would the reaction shift?

a. A decrease in temperature will cause the reaction to shift toward the endothermic reaction, which has the reactants MgCl2 and H2.
b. A decrease in temperature will cause the reaction to shift toward the endothermic reaction, which has the reactants Mg and HCl.
c. A decrease in temperature will cause the reaction to shift toward the exothermic reaction, which has the reactants Mg and HCl.
d. A decrease in temperature will cause the reaction to shift toward the exothermic reaction, which has the reactants MgCl2 and H2.