1) Sn+2NaOH+4H2O=2H2+Na2[Sn(OH)6]
2) 3H2S+K2Cr2O7 + 7H2SO4 = 3S+Cr2(SO4)3 + 7Н2О
3) 3Cl2+6KOH=KClO3 +5KCl+3Н2О
4) 2H2S+H2SO3=3S+3H2O