41 bài tập Lập phương trình hóa học phản ứng oxi hóa - khử (có lời giải)

$\underset{C.K}{\underbrace{H\stackrel{-1}{Cl}}}+\underset{C.OXH}{\underbrace{\stackrel{+4}{Mn}{O}_2}} \stackrel{}{\to }\stackrel{+2}{Mn}C{l}_2+{\stackrel{0}{Cl}}_2+H_{2}O$

$\left.\begin{array}{l}1x\\ 1x\end{array}\right|\left|\begin{array}{l}M{n}^{+4}\text{ + 2e }\stackrel{}{\to }{\text{ Mn}}^{+2}\\ 2C{l}^{-}\stackrel{}{\to }C{l}_2\text{ + 2.1e}\end{array}\right.$

4HCl + MnO₂  MnCl₂ + Cl₂ + 2H₂O

$\underset{C.OXH}{\underbrace{K\stackrel{+7}{Mn}{O}_4}}+\underset{C.K}{\underbrace{K\stackrel{+3}{N}{O}_2}}+H_{2}S{O}_4 \stackrel{}{\to }\stackrel{+2}{Mn}S{O}_4+K\stackrel{+5}{N}{O}_3+K_{2}S{O}_4+H_{2}O$

$\left.\begin{array}{l}2x\\ 5x\end{array}\right|\left|\begin{array}{l}M{n}^{+7}\text{ + 5e }\stackrel{}{\to }{\text{ Mn}}^{+2}\\ N^{+3}\stackrel{}{\to }{N}^{+5}\text{ + 2e}\end{array}\right.$

2KMnO₄ + 5KNO₂ + 3H₂SO₄  2MnSO₄ + 5KNO₃ + K₂SO₄ + 3H₂O

$\underset{C.K}{\underbrace{{\stackrel{\text{+8/3}}{Fe}}_3{O}_4}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}} \stackrel{}{\to }\stackrel{+3}{Fe}{\left(N{O}_3\right)}_3+\stackrel{+2}{N}O+H_{2}O$

$\left.\begin{array}{l}1x\\ 3x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 3e }\stackrel{}{\to }{\text{ N}}^{+2}\\ \text{ 3}F{e}^{+\text{8/3}}\stackrel{}{\to }3F{e}^{+3}\text{ + 1e}\end{array}\right.$

3Fe₃O₄ + 28HNO₃  3Fe(NO₃)₃ + NO + 14H₂O

$\underset{C.K}{\underbrace{H_2{\stackrel{+3}{C}}_2{O}_4}}+\underset{C.OXH}{\underbrace{K\stackrel{+7}{Mn}{O}_4}}+H_{2}S{O}_4 \stackrel{}{\to }\stackrel{+4}{C}{O}_2+\stackrel{+2}{Mn}S{O}_4+K_{2}S{O}_4+H_{2}O$

$\left.\begin{array}{l}2x\\ 5x\end{array}\right|\left|\begin{array}{l}M{n}^{+7}\text{ + 5e }\stackrel{}{\to }{\text{ Mn}}^{+2}\\ C_2^{+3}\stackrel{}{\to }2C^{+4}\text{ + 2.1e}\end{array}\right.$

5H₂C₂O₄ + 2KMnO₄ + 3H₂SO₄  10CO₂ + 2MnSO₄ + K₂SO₄ + 8H₂O

$\underset{C.K}{\underbrace{\stackrel{0}{Zn}}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}} \stackrel{}{\to }\stackrel{+2}{Zn}{\left(N{O}_3\right)}_2+\stackrel{+2}{N}O+H_{2}O$

$\left.\begin{array}{l}2x\\ 3x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 3e }\stackrel{}{\to }{\text{ N}}^{+2}\\ Z{n}^0\stackrel{}{\to }Z{n}^{+2}\text{ + 2e}\end{array}\right.$

3Zn + 8HNO₃  3Zn(NO₃)₂ + 2NO + 4H₂O

$\underset{C.OXH}{\underbrace{K_2{\stackrel{+6}{Cr}}_2{O}_7}}+\underset{C.K}{\underbrace{H\stackrel{-1}{Cl}}}\stackrel{}{\to }KCl+\stackrel{+3}{Cr}C{l}_3+{\stackrel{0}{Cl}}_2+H_{2}O$

$\left.\begin{array}{l}1x\\ 3x\end{array}\right|\left|\begin{array}{l}\text{ 2}C{r}^{+6}\text{ + 2.3e }\stackrel{}{\to }2C{r}^{+3}\\ 2C{l}^{-}\stackrel{}{\to }C{l}_2\text{ + 2.1e}\end{array}\right.$

K₂Cr₂O₇ + 14HCl  2KCl + 2CrCl₃ + 3Cl₂ + 7H₂O

$\underset{C.K}{\underbrace{\stackrel{0}{Cu}}}+\underset{C.OXH}{\underbrace{H_2\stackrel{+6}{S}{O}_4}}\stackrel{}{\to } \stackrel{+2}{Cu}S{O}_4+\stackrel{+4}{S}{O}_2+H_{2}O$

$\left.\begin{array}{l}1x\\ 1x\end{array}\right|\left|\begin{array}{l}{S}^{+6}\text{ + 2e }\stackrel{}{\to }{\text{ S}}^{+4}\\ C{u}^0\stackrel{}{\to }C{u}^{+2}\text{ + 2e}\end{array}\right.$

Cu + 2H₂SO_{4 (đặc)}  CuSO₄ + SO₂ + 2H₂O

$\underset{C.K}{\underbrace{\stackrel{0}{Al}}}+\underset{C.OXH}{\underbrace{H_2\stackrel{+6}{S}{O}_4}}\stackrel{}{\to }{\stackrel{+3}{Al}}_2{\left(S{O}_4\right)}_3+\stackrel{+4}{S}{O}_2+H_{2}O$

$\left.\begin{array}{l}3x\\ 2x\end{array}\right|\left|\begin{array}{l}{S}^{+6}\text{ + 2e }\stackrel{}{\to }{\text{ S}}^{+4}\\ A{l}^0\stackrel{}{\to }A{l}^{+3}\text{ + 3e}\end{array}\right.$

2Al + 6H₂SO_{4 (đặc)}  Al₂(SO₄)₃ + 3SO₂ + 6H₂O

$\underset{C.K}{\underbrace{\stackrel{0}{Mg}}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }\stackrel{+2}{Mg}{\left(N{O}_3\right)}_2+\stackrel{-3}{N}{H}_{4}N{O}_3+H_{2}O$

$\left.\begin{array}{l}1x\\ 4x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 8e }\stackrel{}{\to }{N}^{-3}\\ M{g}^0\stackrel{}{\to }M{g}^{+2}\text{ + 2e}\end{array}\right.$

4Mg + 10HNO₃  4Mg(NO₃)₂ + NH₄NO₃ + 3H₂O

$\underset{C.K}{\underbrace{\stackrel{0}{Fe}}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }\stackrel{+3}{Fe}{\left(N{O}_3\right)}_3+\stackrel{+4}{N}{O}_2+H_{2}O$

$\left.\begin{array}{l}3x\\ 1x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 1e }\stackrel{}{\to }{N}^{+4}\\ F{e}^0\stackrel{}{\to }{\text{ Fe}}^{+3}\text{ + 3e}\end{array}\right.$

Fe + 6HNO₃  Fe(NO₃)₃ + 3NO₂ + 3H₂O

$\underset{C.K}{\underbrace{\stackrel{0}{Zn}}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }\stackrel{+2}{Zn}{\left(N{O}_3\right)}_2+{\stackrel{+1}{N}}_{2}O+H_{2}O$

$\left.\begin{array}{l}1x\\ 4x\end{array}\right|\left|\begin{array}{l}\text{ 2}{N}^{+5}\text{ + 2.4e }\stackrel{}{\to }{N}_2^{+1}\\ Z{n}^0\stackrel{}{\to }Z{n}^{+2}\text{ + 2e}\end{array}\right.$

4Zn + 10HNO₃  4Zn(NO₃)₂ + N₂O + 5H₂O

$\underset{C.K+C.OXH}{\underbrace{Cu{\left(\stackrel{+5}{N}{\stackrel{-2}{O}}_3\right)}_2}}\stackrel{}{\to }CuO+\stackrel{+4}{N}{O}_2+{\stackrel{0}{O}}_2$

$\left.\begin{array}{l}4x\\ 1x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 1e }\stackrel{}{\to }{N}^{+4}\\ 2O^{-2}\stackrel{}{\to }{O}_2\text{ + 2.2e}\end{array}\right.$

2Cu(NO₃)₂  CuO + 4NO₂ + O₂

$\underset{C.K+OXH}{\underbrace{{\stackrel{0}{Cl}}_2}}+KOH\stackrel{}{\to }K\stackrel{-1}{Cl}+K\stackrel{+5}{Cl}{O}_3+H_{2}O$

$\left.\begin{array}{l}5x\\ 1x\end{array}\right|\left|\begin{array}{l}C{l}^0\text{ + 1e }\stackrel{}{\to }C{l}^{-}\\ C{l}^0\stackrel{}{\to }C{l}^{+5}\text{ + 5e}\end{array}\right.$

3Cl₂ + 6KOH  5KCl + KClO₃ + 3H₂O

$\underset{C.K+OXH}{\underbrace{\stackrel{+4}{N}{O}_2}}+NaOH\stackrel{}{\to }Na\stackrel{+3}{N}{O}_2+Na\stackrel{+5}{N}{O}_3+H_{2}O$

$\left.\begin{array}{l}1x\\ 1x\end{array}\right|\left|\begin{array}{l}{N}^{+4}\text{ + 1e }\stackrel{}{\to }{N}^{+3}\\ N^{+4}\stackrel{}{\to }{N}^{+5}\text{ + 1e}\end{array}\right.$

2NO₂ + 2NaOH  NaNO₂ + NaNO₃ + H₂O

$\underset{C.K+OXH}{\underbrace{K\stackrel{+5}{Cl}{\stackrel{-2}{O}}_3}}\stackrel{}{\to }K\stackrel{-1}{Cl}+{\stackrel{0}{O}}_2$

$\left.\begin{array}{l}2x\\ 3x\end{array}\right|\left|\begin{array}{l}C{l}^{+5}\text{ + 6e }\stackrel{}{\to }C{l}^{-}\\ 2O^{-2}\stackrel{}{\to }{O}_2\text{ + 2.2e}\end{array}\right.$

2KClO₃  2KCl + 3O₂

$\underset{C.K+OXH}{\underbrace{K\stackrel{+7}{Mn}{\stackrel{-2}{O}}_4}}\stackrel{}{\to }{K}_2\stackrel{+6}{Mn}{O}_4+\stackrel{+4}{Mn}{O}_2+O_2$

$\left.\begin{array}{l}1x\\ 1x\end{array}\right|\left|\begin{array}{l}2M{n}^{+7}\text{ + 4e }\stackrel{}{\to }{\text{ Mn}}^{+6}{\text{ + Mn}}^{+4}\\ 2O^{-2}\stackrel{}{\to }{O}_2\text{ + 2.2e}\end{array}\right.$

2KMnO₄  K₂MnO₄ + MnO₂ + O_2­

$\underset{C.K+OXH}{\underbrace{Na\stackrel{+5}{N}{\stackrel{-2}{O}}_3}}\stackrel{}{\to }Na\stackrel{+3}{N}{O}_2+{\stackrel{0}{O}}_2$

$\left.\begin{array}{l}2x\\ 1x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 2e }\stackrel{}{\to }{\text{ N}}^{+3}\\ 2O^{-2}\stackrel{}{\to }{O}_2\text{ + 2.2e}\end{array}\right.$

2NaNO₃  2NaNO₂ + O₂

$\underset{C.K+OXH}{\underbrace{\stackrel{-3}{N}{H}_4\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }{\stackrel{+1}{N}}_{2}O+H_{2}O$

$\left.\begin{array}{l}1x\\ 1x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 4e }\stackrel{}{\to }{\text{ N}}^{+1}\\ N^{-3}\stackrel{}{\to }{N}^{+1}\text{ + 4e}\end{array}\right.$

NH₄NO₃  N₂O + 2H₂O

$\underset{C.K}{\underbrace{{\stackrel{+2y/x}{Fe}}_x{O}_y}}+\underset{C.OXH}{\underbrace{H_2\stackrel{+6}{S}{O}_4}}\stackrel{}{\to }{\stackrel{+3}{Fe}}_2{\left(S{O}_4\right)}_3+\stackrel{+4}{S}{O}_2+H_{2}O$

$\left.\begin{array}{l}\text{(3x }-\text{ 2y)x}\\ 1x\end{array}\right|\left|\begin{array}{l}{S}^{+6}\text{ + 2e }\stackrel{}{\to }{S}^{+4}\\ \text{ 2}F{e}_x^{+2y/x}\stackrel{}{\to }{\text{ 2xFe}}^{+3}\text{ + 2.(3x }-\text{ 2y)e}\end{array}\right.$

2Fe_xO_y + (6x – 2y)H₂SO₄  xFe₂(SO₄)₃ + (3x – 2y)SO₂ + (6x – 2y)H₂O

$\underset{C.K}{\underbrace{\stackrel{+2}{Fe}{\stackrel{-1}{S}}_2}}+\underset{C.OXH}{\underbrace{{\stackrel{0}{O}}_2}}\stackrel{}{\to }{\stackrel{+3}{Fe}}_2{\stackrel{-2}{O}}_3+\stackrel{+4}{S}{O}_2$

$\left.\begin{array}{l}11x\\ 2x\end{array}\right|\left|\begin{array}{l}{O}_2\text{ + 2.2e }\stackrel{}{\to }2O^{-2}\\ \text{ 2}\stackrel{+2}{Fe}{\stackrel{-1}{S}}_2\stackrel{}{\to }2F{e}^{3+}{\text{ + 4S}}^{+4}\text{ + 22e}\end{array}\right.$

4FeS₂ + 11O₂  2Fe₂O₃ + 8SO₂

$\underset{C.K}{\underbrace{\stackrel{+2}{Fe}{\stackrel{-1}{S}}_2}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }\stackrel{+3}{Fe}{\left(N{O}_3\right)}_3+H_2\stackrel{+6}{S}{O}_4+\stackrel{+2}{N}O+H_{2}O$

$\left.\begin{array}{l}5x\\ 1x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 3e }\stackrel{}{\to }{N}^{+2}\\ \stackrel{+2}{Fe}{\stackrel{-1}{S}}_2\stackrel{}{\to }F{e}^{3+}{\text{ + 2S}}^{+6}\text{ + 15e}\end{array}\right.$

FeS₂ + 8HNO₃  Fe(NO₃)₃ + 2H₂SO₄ + 5NO + 2H₂O

$\underset{C.K}{\underbrace{{\stackrel{+1}{Cu}}_2\stackrel{-2}{S}}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }\stackrel{+2}{Cu}{\left(N{O}_3\right)}_2+Cu\stackrel{+6}{S}{O}_4+\stackrel{+2}{N}O+H_{2}O$

$\left.\begin{array}{l}10x\\ 3x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 3e }\stackrel{}{\to }{N}^{+2}\\ {\stackrel{+1}{Cu}}_2\stackrel{-2}{S}\stackrel{}{\to }\text{ 2}C{u}^{+2}{\text{ + S}}^{+6}\text{ + 10e}\end{array}\right.$

3Cu₂S + 16HNO₃  3Cu(NO₃)₂ + 3CuSO₄ + 10NO + 8H₂O

$\underset{C.K}{\underbrace{\stackrel{0}{M}}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }\stackrel{+n}{M}{\left(N{O}_3\right)}_n+\stackrel{+2}{N}O+H_{2}O$

$\left.\begin{array}{l}nx\\ 3x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 3e }\stackrel{}{\to }{N}^{+2}\\ M^0\stackrel{}{\to }{\text{ M}}^{+n}\text{ + ne}\end{array}\right.$

3M + 4nHNO₃  3M(NO₃)_n + nNO + 2nH₂O

$\underset{C.K}{\underbrace{\stackrel{0}{Al}}}+\underset{C.K}{\underbrace{H\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }\stackrel{+3}{Al}{\left(N{O}_3\right)}_3+{\stackrel{+2y/x}{N}}_x{O}_y+H_{2}O$

$\left.\begin{array}{l}3x\\ \text{(3x }-\text{ 2y)}x\end{array}\right|\left|\begin{array}{l}\text{ x}{N}^{+5}\text{ + (3x }-\text{ 2y)e }\stackrel{}{\to }{N}_x^{+2y/x}\\ A{l}^0\stackrel{}{\to }{\text{ Al}}^{+3}\text{ + 3e}\end{array}\right.$

(3x – 2y)Al + (12x – 6y)HNO₃  (3x – 2y)Al(NO₃)₃ + 3N_xO_y + (6x – 3y)H₂O

$\underset{C.K}{\underbrace{\stackrel{0}{R}}}+\underset{C.OXH}{\underbrace{H_2\stackrel{+6}{S}{O}_4}}\stackrel{}{\to }{\stackrel{+n}{R}}_2{\left(S{O}_4\right)}_n+\stackrel{+4}{S}{O}_2+H_{2}O$

$\left.\begin{array}{l}nx\\ 2x\end{array}\right|\left|\begin{array}{l}{S}^{+6}\text{ + 2e }\stackrel{}{\to }{\text{ S}}^{+4}\\ R^0\stackrel{}{\to }{R}^{+n}\text{ + ne}\end{array}\right.$

2R + 2nH₂SO_{4 (đặc)}  R₂(SO₄)_n + nSO₂ + 2nH₂O

$\underset{C.K}{\underbrace{{\stackrel{+2y/x}{Fe}}_x{O}_y}}+\underset{C.OXH}{\underbrace{H\stackrel{+5}{N}{O}_3}}\stackrel{}{\to }\stackrel{+3}{Fe}{\left(N{O}_3\right)}_3+\stackrel{+4}{N}{O}_2+H_{2}O$

$\left.\begin{array}{l}\text{(3x }-\text{ 2y)x}\\ 1x\end{array}\right|\left|\begin{array}{l}{N}^{+5}\text{ + 1e }\stackrel{}{\to }{N}^{+4}\\ F{e}_x^{+2y/x}\stackrel{}{\to }{\text{ xFe}}^{+3}\text{ + (3x }-\text{ 2y)e}\end{array}\right.$

Fe_xO_y + (6x – 2y)HNO₃  xFe(NO₃)₃ + (3x – 2y)NO₂ + (3x – y)H₂O