А) 3Sn2+ -6e- + 2H2O + 12Cl- = SnO2 + 2H2[SnCl6] | 6 | 6 | 1 | - восст-ь
(BrO3)- +6e- + 6H+ = Br- + 3H2O | 6 | | 1 | - окис-ь;
3Sn2+ + (BrO3)- + 6H+ + 12Cl- = SnO2 + 2H2[SnCl6] + Br- + H2O;
3SnCl2 + KBrO3 + 6HCl = SnO2 + 2H2[SnCl6] + KBr + H2O;
б) 2Fe2+ -2e- = 2Fe3+ | 2 | 6 | 3 | - восст-ь
(ClO3)- +6e- + 6H+ = Cl- + 3H2O | 6 | | 1 | - окис-ь;
6Fe2+ + (ClO3)- + 6H+ = 6Fe3+ + Cl- + 3H2O;
6FeSO4 + KClO3 + 3H2SO4 = 3Fe2(SO4)3 + KCl + 3H2O.
4Na+O2-->2Na2O
2Na(0) -2ē--->2Na(+)
O2(0) +4ē--->2O(-2)
1. w(Mg)=M(Mg):M(MgO)*100%=24:(24+16)*100%=60%
w(O)=M(O):M(MgO)*100%=16:(24+16)*100%=40%
2. w(Cu)=M(Cu):M(CuSO4)*100%=64:(64+32+16*4)*100%=40%
w(S)=M(S):M(CuSO4)*100%=32:(64+32+16*4)*100%=20%
w(O)=M(O4);M(CuSo4)*100%=16*4:(64+32+16*4)*100%=20%
3Сu + 8HNO3 -> 3Cu(NO3)2 + 2NO + 4H2O
Cu(0) -2e -> Cu(+2) 3 ок-ие
в-ль
N(+5) +3e -> N(+2) 2 в-ие
ок-ль