41 bài tập Lập phương trình hóa học phản ứng oxi hóa - khử (có lời giải)
41 câu hỏi
Cân bằng các phản ứng oxi hóa – khử sau (dạng cơ bản)
(1) Fe2O3+ CO → Fe + CO2
Fe+32O3⏟C.OXH+ C+2O⏟C.K → Fe + CO2
1x3x 2Fe+3 + 2.3e → 2Fe0 C+2 → C+4 + 2e
Fe2O3 + 3CO 2Fe + 3CO2
(2) NH3 + O2 NO + H2O
4NH3 + 5O2 4NO + 6H2O
(3) NaBr + Cl2 NaCl + Br2
2NaBr + Cl2 2NaCl + Br2
(4) Cr(OH)3 + Br2 + OH− → CrO42− + Br− + H2O
Cr+3(OH)3⏟C.K + Br02⏟C.OXH + OH− → Cr+6O42− + Br− + H2O
3x2x Br2 + 2.1e → 2Br− Cr+3 → Cr+6 + 3e
2Cr(OH)3 + 3Br2 + 10OH− → 2CrO42− + 6Br− + 8H2O
(5) H+ + MnO4− + HCOOH → Mn2+ + H2O + CO2
H+ + Mn+7O4− + HC+2OOH → Mn+2 + H2O + C+4O2
2x5x Mn7+ + 5e → Mn2+ C2+ → C4+ + 2e
6H+ + 2MnO4− + 5HCOOH → 2Mn2+ + 8H2O + 5CO2
(6) KI + Br2 KBr + I2
2KI + Br2 2KBr + I2
(7) NO2 + O2 + H2O HNO3
4NO2 + O2 + 2H2O 4HNO3
(8) C + HNO3 CO2 + NO + H2O
C + 4HNO3 4CO2 + NO + 2H2O
(9) SO2 + Br2 + H2O H2SO4 + HBr
SO2 + Br2 + 2H2O H2SO4 + 2HBr
(10) H2S + O2 S + H2O
2H2S + O2 2S + 2H2O
(11) P + HNO3 H3PO4 + NO2 + H2O
P + 5HNO3 H3PO4 + 5NO2 + H2O
(12) H2S + SO2 S + H2O
2H2S + SO2 3S + 2H2O
Cân bằng các phản ứng oxi hóa – khử sau (dạng môi trường):
(1) HCl + PbO2 PbCl2 + Cl2 + H2O
HCl−1⏟C.K + Pb+4O2⏟C.OXH → Pb+2Cl2+ Cl02+ H2O
1x1x Pb+4 + 2e → Pb+2 2Cl− → Cl2 + 2.1e
4HCl + PbO2 PbCl2 + Cl2 + 2H2O
(2) KMnO4 + HCl KCl + MnCl2 + Cl2 + H2O
KMn+7O4⏟C.OXH+ HCl−1⏟C.K → KCl + Mn+2Cl2+ Cl02+ H2O
2x5x Mn+7 + 5e → Mn+2 2Cl− → Cl2 + 2.1e
2KMnO4 + 16HCl 2KCl + 2MnCl2 + 5Cl2 + 8H2O
(3) HCl + MnO2 MnCl2 + Cl2 + H2O
HCl−1⏟C.K + Mn+4O2⏟C.OXH → Mn+2Cl2+ Cl02+ H2O
1x1x Mn+4 + 2e → Mn+2 2Cl− → Cl2 + 2.1e
4HCl + MnO2 MnCl2 + Cl2 + 2H2O
(4) KMnO4 + KNO2 + H2SO4 MnSO4 + KNO3 + K2SO4 + H2O
KMn+7O4⏟C.OXH+ KN+3O2⏟C.K+ H2SO4 → Mn+2SO4+ KN+5O3+ K2SO4+ H2O
2x5x Mn+7 + 5e → Mn+2 N+3 → N+5 + 2e
2KMnO4 + 5KNO2 + 3H2SO4 2MnSO4 + 5KNO3 + K2SO4 + 3H2O
(5) Fe3O4 + HNO3 Fe(NO3)3 + NO + H2O
Fe+8/33O4⏟C.K+ HN+5O3⏟C.OXH → Fe+3(NO3)3+ N+2O + H2O
1x3x N+5 + 3e → N+2 3Fe+8/3 → 3Fe+3 + 1e
3Fe3O4 + 28HNO3 3Fe(NO3)3 + NO + 14H2O
(6) H2C2O4 + KMnO4 + H2SO4 CO2 + MnSO4 + K2SO4 + H2O
H2C+32O4⏟C.K+ KMn+7O4⏟C.OXH+ H2SO4 → C+4O2+ Mn+2SO4+ K2SO4+ H2O
2x5x Mn+7 + 5e → Mn+2 C2+3 → 2C+4 + 2.1e
5H2C2O4 + 2KMnO4 + 3H2SO4 10CO2 + 2MnSO4 + K2SO4 + 8H2O
(7) Zn + HNO3 Zn(NO3)2 + NO + H2O
Zn0⏟C.K + HN+5O3⏟C.OXH → Zn+2(NO3)2+ N+2O + H2O
2x3x N+5 + 3e → N+2 Zn0 → Zn+2 + 2e
3Zn + 8HNO3 3Zn(NO3)2 + 2NO + 4H2O
(8) K2Cr2O7 + HCl KCl + CrCl3 + Cl2 + H2O
K2Cr+62O7⏟C.OXH+ HCl−1⏟C.K → KCl + Cr+3Cl3+ Cl02+ H2O
1x3x 2Cr+6 + 2.3e → 2Cr+3 2Cl− → Cl2 + 2.1e
K2Cr2O7 + 14HCl 2KCl + 2CrCl3 + 3Cl2 + 7H2O
(9) Cu + H2SO4 (đặc) CuSO4 + SO2 + H2O
Cu0⏟C.K + H2S+6O4⏟C.OXH → Cu+2SO4+ S+4O2+ H2O
1x1x S+6 + 2e → S+4 Cu0 → Cu+2 + 2e
Cu + 2H2SO4 (đặc) CuSO4 + SO2 + 2H2O
(10) Al + H2SO4 (đặc) Al2(SO4)3 + SO2 + H2O
Al0⏟C.K + H2S+6O4⏟C.OXH → Al+32(SO4)3+ S+4O2+ H2O
3x2x S+6 + 2e → S+4 Al0 → Al+3 + 3e
2Al + 6H2SO4 (đặc) Al2(SO4)3 + 3SO2 + 6H2O
(11) Mg + HNO3 Mg(NO3)2 + NH4NO3 + H2O
Mg0⏟C.K + HN+5O3⏟C.OXH → Mg+2(NO3)2+ N−3H4NO3+ H2O
1x4x N+5 + 8e → N−3 Mg0 → Mg+2 + 2e
4Mg + 10HNO3 4Mg(NO3)2 + NH4NO3 + 3H2O
(12) Fe + HNO3 Fe(NO3)3 + NO2 + H2O
Fe0⏟C.K + HN+5O3⏟C.OXH → Fe+3(NO3)3+ N+4O2+ H2O
3x1x N+5 + 1e → N+4 Fe0 → Fe+3 + 3e
Fe + 6HNO3 Fe(NO3)3 + 3NO2 + 3H2O
(13) Zn + HNO3 Zn(NO3)2 + N2O + H2O
Zn0⏟C.K + HN+5O3⏟C.OXH → Zn+2(NO3)2+ N+12O + H2O
1x4x 2N+5 + 2.4e → N2+1 Zn0 → Zn+2 + 2e
4Zn + 10HNO3 4Zn(NO3)2 + N2O + 5H2O
Cân bằng các phản ứng oxi hóa – khử sau (phản ứng tự oxi hóa – khử và nội oxi hóa – khử):
(1) Cu(NO3)2 CuO + NO2 + O2
Cu(N+5O−23)2⏟C.K+C.OXH → CuO + N+4O2+ O02
4x1x N+5 + 1e → N+4 2O−2 → O2 + 2.2e
2Cu(NO3)2 CuO + 4NO2 + O2
(2) Cl2 + KOH KCl + KClO3 + H2O
Cl02⏟C.K+OXH + KOH → KCl−1 + KCl+5O3+ H2O
5x1x Cl0 + 1e → Cl− Cl0 → Cl+5 + 5e
3Cl2 + 6KOH 5KCl + KClO3 + 3H2O
(3) NO2 + NaOH NaNO2 + NaNO3 + H2O
N+4O2⏟C.K+OXH+ NaOH → NaN+3O2+ NaN+5O3+ H2O
1x1x N+4 + 1e → N+3 N+4 → N+5 + 1e
2NO2 + 2NaOH NaNO2 + NaNO3 + H2O
(4) Cl2 + KOH KCl + KClO + H2O
Cl02⏟C.K+OXH + KOH → KCl−1 + KCl+1O+ H2O
1x1x Cl0 + 1e → Cl− Cl0 → Cl+1 + 1e
Cl2 + 2KOH KCl + KClO + H2O
(5) KClO3 KCl + O2
KCl+5O−23⏟C.K+OXH → KCl−1 + O02
2x3x Cl+5 + 6e → Cl− 2O−2 → O2 + 2.2e
2KClO3 2KCl + 3O2
(6) KMnO4 K2MnO4 + MnO2 + O2
KMn+7O−24⏟C.K+OXH → K2Mn+6O4+ Mn+4O2+ O2
1x1x 2Mn+7 + 4e → Mn+6 + Mn+4 2O−2 → O2 + 2.2e
2KMnO4 K2MnO4 + MnO2 + O2
(7) NaNO3 NaNO2 + O2
NaN+5O−23⏟C.K+OXH → NaN+3O2+ O02
2x1x N+5 + 2e → N+3 2O−2 → O2 + 2.2e
2NaNO3 2NaNO2 + O2
(8) NH4NO3 N2O + H2O
N−3H4N+5O3⏟C.K+OXH → N+12O + H2O
1x1x N+5 + 4e → N+1 N−3 → N+1 + 4e
NH4NO3 N2O + 2H2O
Cân bằng các phản ứng oxi hóa – khử sau (dạng phức tạp):
(1) FexOy + H2SO4 Fe2(SO4)3 + SO2 + H2O
Fe+2y/xxOy⏟C.K+ H2S+6O4⏟C.OXH → Fe+32(SO4)3+ S+4O2+ H2O
(3x − 2y)x1x S+6 + 2e → S+4 2Fex+2y/x → 2xFe+3 + 2.(3x − 2y)e
2FexOy + (6x – 2y)H2SO4 xFe2(SO4)3 + (3x – 2y)SO2 + (6x – 2y)H2O
(2) FeS2 + O2 Fe2O3 + SO2
Fe+2S−12⏟C.K + O02⏟C.OXH → Fe+32O−23 + S+4O2
11x2x O2 + 2.2e → 2O−2 2Fe+2S−12 → 2Fe3+ + 4S+4 + 22e
4FeS2 + 11O2 2Fe2O3 + 8SO2
(3) FeS2 + HNO3 Fe(NO3)3 + H2SO4 + NO + H2O
Fe+2S−12⏟C.K+ HN+5O3⏟C.OXH → Fe+3(NO3)3+ H2S+6O4+ N+2O + H2O
5x1x N+5 + 3e → N+2 Fe+2S−12 → Fe3+ + 2S+6 + 15e
FeS2 + 8HNO3 Fe(NO3)3 + 2H2SO4 + 5NO + 2H2O
(4) Cu2S + HNO3 Cu(NO3)2 + CuSO4 + NO + H2O
Cu+12S−2⏟C.K + HN+5O3⏟C.OXH → Cu+2(NO3)2+ CuS+6O4+ N+2O + H2O
10x3x N+5 + 3e → N+2 Cu+12S−2 → 2Cu+2 + S+6 + 10e
3Cu2S + 16HNO3 3Cu(NO3)2 + 3CuSO4 + 10NO + 8H2O
(5) M + HNO3 M(NO3)n + NO + H2O
M0⏟C.K + HN+5O3⏟C.OXH → M+n(NO3)n+ N+2O + H2O
nx3x N+5 + 3e → N+2 M0 → M+n + ne
3M + 4nHNO3 3M(NO3)n + nNO + 2nH2O
(6) Al + HNO3 Al(NO3)3 + NxOy + H2O
Al0⏟C.K + HN+5O3⏟C.K → Al+3(NO3)3+ N+2y/xxOy+ H2O
3x(3x − 2y)x xN+5 + (3x − 2y)e → Nx+2y/x Al0 → Al+3 + 3e
(3x – 2y)Al + (12x – 6y)HNO3 (3x – 2y)Al(NO3)3 + 3NxOy + (6x – 3y)H2O
(7) R + H2SO4 (đặc) R2(SO4)n + SO2 + H2O
R0⏟C.K + H2S+6O4⏟C.OXH → R+n2(SO4)n+ S+4O2+ H2O
nx2x S+6 + 2e → S+4 R0 → R+n + ne
2R + 2nH2SO4 (đặc) R2(SO4)n + nSO2 + 2nH2O
(8) FexOy + HNO3 Fe(NO3)3 + NO2 + H2O
Fe+2y/xxOy⏟C.K+ HN+5O3⏟C.OXH → Fe+3(NO3)3+ N+4O2+ H2O
(3x − 2y)x1x N+5 + 1e → N+4 Fex+2y/x → xFe+3 + (3x − 2y)e
FexOy + (6x – 2y)HNO3 xFe(NO3)3 + (3x – 2y)NO2 + (3x – y)H2O
