Zn + 2HCl =ZnCl2 + H2
3ZnCl2 +2Al =3Zn +2 AlCl3
Mg + H2SO4=Mg SO4 + H2
Zn + Cl2=ZnCl2
a=ZnCl2
b=H2
c=AlCl3
d=Cl2