In the voltaic cell reaction below, what is reduced and what is the cathode? Ag+(aq) is reduced and Ag is the cathode. Ag+(aq) is reduced and Mg is the cathode. Mg(s) is reduced and Ag is the cathode. Mg(s) is reduced and Mg is the cathode. A system in which electricity is used to cause a chemical reaction is called a(n) electrolytic cell. spontaneous system. voltaic cell. enzymatic reaction