1,C +2H2SO4->C02+2SO2 +2H2O 

2,P +5HNO3 ->H3P4O +5NO2 +H20 

3, 2PH3 +4O2 ->P2O5+3H2O 

4,4NH3 +5O2 ->4NO+6H2O 

5,SO2+Br2 +2H2O -> 2HBr +H2SO4 

6, 2KClO3+3C -> 2KCl +3CO2 

7, 3P +5HNO3 +2H2O -> 3H3PO4 +5NO  

8,2PH3 +4O2 ->P2O5+3H2O 

9, CH4 +2O2 -> CO2+ 2H2O

1)

N^-3 \(\rightarrow\) N⁺² + 5e (4x)

2O+ 4e\(\rightarrow\) 2O^-2 (5x)

4NH3+ 5O2\(\underrightarrow{^{to}}\) 4NO+ 6H2O

2)

2N^-3 \(\rightarrow\) N2 + 6e (2x)

2O + 4e \(\rightarrow\)2O^-2 (3x)

8NH3 + 6O2\(\underrightarrow{^{to}}\)4N2+ 12H2O

3)

S^-2 \(\rightarrow\) S + 2e (2x)

2O+ 4e \(\rightarrow\) 2O^-2 (1x)

2H2S+ O2 \(\underrightarrow{^{to}}\)2S+ 2H2O

4)

2P \(\rightarrow\) 2P⁺⁵ +10e (6x)

Cl⁺⁵ +6e\(\rightarrow\) Cl^-1 (5x)

6P+ 5KClO3 \(\underrightarrow{^{to}}\) 3P2O5+ 5KCl

(1) \(K\overset{+7}{Mn}O_4+H\overset{-1}{Cl}\rightarrow KCl+\overset{+2}{Mn}Cl_2+\overset{0}{Cl_2}+H_2O\)

- Chất khử: HCl

Chất oxh: KMnO₄

- Sự oxh: \(2Cl^{-1}\rightarrow Cl_2^0+2e|\times5\)

Sự khử: \(Mn^{+7}+5e\rightarrow Mn^{+2}|\times2\)

\(\rightarrow2KMnO_4+16HCl\rightarrow2KCl+2MnCl_2+5Cl_2+8H_2O\)

(2) \(H\overset{+5}{N}O_3+\overset{0}{Cu}\rightarrow\overset{+2}{Cu}\left(NO_3\right)_2+\overset{+4}{N}O_2+H_2O\)

- Chất khử: Cu

Chất oxh: HNO₃

- Sự khử: \(N^{+5}+1e\rightarrow N^{+4}|\times2\)

Sự oxh: \(Cu^0\rightarrow Cu^{+2}+2e|\times1\)

\(\rightarrow4HNO_3+Cu\rightarrow Cu\left(NO_3\right)_2+2NO_2+2H_2O\)

(3) \(\overset{-3}{N}H_3+\overset{0}{O_2}\rightarrow\overset{+2}{N}\overset{-2}{O}+H_2O\)

- Chất khử: NH₃

 Chất oxh: O₂

- Sự khử: \(O_2^0+4e\rightarrow2O^{-2}|\times5\)

Sự oxh: \(N^{-3}\rightarrow N^{+2}+5e|\times4\)

\(\rightarrow4NH_3+5O_2\rightarrow4NO+6H_2O\)

Cân bằng các phương trình phản ứng oxi hóa – khử:

U

Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O 

3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O 

NH₄NO₃ → N₂O + 2H₂O

NH₄NO₂ → N₂ + 2H₂O

2AgNO₃ →  2Ag + O₂ + 2NO₂

b)

$S^{-2} + 2e \to S^0$
$N^{+5} \to N^{+2} + 3e$

$3H_2S + 2HNO_3 \to 3S + 2NO + 4H_2O$

c)

$Mg^0 \to Mg^{+2} + 2e$
$N^{+5} + 3e \to N^{+2}$
$3Mg + 8HNO_3 \to 3Mg(NO_3)_2 + 2NO + 4H_2O$

e)

$Al^0 \to Al^{+3} + 3e$
$S^{+6} + 2e \to S^{+4}$
$2Al + 6H_2SO_4 \to Al_2(SO_4)_3 + 3SO_2 + 6H_2O$

g)

$Cu_2S \to 2Cu^{+2} + S^{+6} + 10e$
$N^{+5} + 3e \to N^{+2}$

$3Cu_2S + 16HNO_3 \to 3Cu(NO_3)_2 + 3CuSO_4 + 10NO + 8H_2O$