a中,负极Mg,正极C,电池反应式为Mg +2H + =Mg 2+ +H 2 ↑
b中,负极Fe,正极Cu,电池反应式为Fe+ 2Fe 3+ =3Fe 2+
c中,负极Al,正极Mg,电池反应式为2Al+2NaOH+2H 2 O=2NaAlO 2 +3H 2 ↑
d中,负极Fe,正极Cu,电池反应式为2Fe+2H 2 O+O 2 =2Fe(OH) 2
e中,负极Cu,正极Ag,电池反应式为Cu +2Ag + =Cu 2+ + 2Ag
f中,负极Mg,正极Al,电池反应式为Mg+2H + =Mg 2+ +H 2 ↑