1)Zn+H2SO4=ZnSO4+H2↑ 2)AL+HCL=2Al + 6HCl = 2AlCl3 + 3H2 3)Pb+H3PO4=3 Pb + 2 H3PO4 = 3 H2 + Pb3(PO4)2 4)2Au +2HI= 2AuI + H2↑