1. Chất khử: Al

Chất oxi hóa: HNO₃      

\(Al\rightarrow Al^{3+}+3e|\times8\\ N^{+5}+8e\rightarrow N^{-3}|\times3\)

8Al  + 30HNO₃   → 8Al(NO₃)₃ + 3NH₄NO₃ + 9H₂O.

2. Chất khử: Mg

Chất oxi hóa: HNO₃      

\(Mg\rightarrow Mg^{2+}+2e|\times3\\ N^{+5}+3e\rightarrow N^{+2}|\times2\)

3Mg + 8HNO₃   → 3Mg(NO₃)₂ + 2NO + 4H₂O.

3. Chất khử: Mg

Chất oxi hóa: H₂SO₄

\(Mg\rightarrow Mg^{2+}+2e|\times8\\ S^{+6}+8e\rightarrow S^{-2}|\times2\)

8Mg +  10H₂SO₄   → 8MgSO₄ + 2H₂S + 8H₂O.

4.Chất khử: Fe

Chất oxi hóa: H₂SO₄ 

\(2Fe\rightarrow Fe^{3+}_2+6e|\times1\\ S^{+6}+2e\rightarrow S^{+4}|\times3\)

2Fe  +  6H₂SO₄   →  Fe₂ (SO₄)₃ + 3SO₂ + 6H₂O.

b

1.Al\(\rightarrow\)Al+3 +3e_______________.(5x-2y)

xN⁺⁵ +(5x-2y)e\(\rightarrow\)xN+\(\frac{2y}{x}\)______.3

\(\rightarrow\)(5x-2y)Al+(18x-6y)HNO3\(\rightarrow\)(5x-2y)Al(NO3)3+3NxOy+(9x-3y)H2O

2.M\(\rightarrow\)M⁺ⁿ +ne____.2

S⁺⁶ +2e\(\rightarrow\)S⁺⁴_____.n

\(\rightarrow\)2M+3nH2SO4\(\rightarrow\)2M(SO4)n+nSO2+3nH2O

3.M\(\rightarrow\)M+n +ne__________.(5x-2y)

xN+5 +(5x-2y)e\(\rightarrow\)xN+\(\frac{2y}{x}\) ____.n

\(\rightarrow\)(5x-2y)M+(6nx-2ny)HNO3\(\rightarrow\)(5x-2y)M(NO3)n+nNxOy+(3nx-ny)H2O

N⁺⁵ +3e\(\rightarrow\)N⁺² __________.1

2N⁺⁵ +8e\(\rightarrow\)2N⁺¹_________ .2

\(\rightarrow\)5N⁺⁵ +19e\(\rightarrow\)N⁺² +4N⁺¹______ .2

Zn\(\rightarrow\)Zn⁺² +2e ____________ .19

\(\rightarrow\)19Zn+48HNO3\(\rightarrow\)19Zn(NO3)2+2NO+4N2O+24H2O

2N⁺⁵ +10e\(\rightarrow\)2N0 .2

2N⁺⁵+ 8e\(\rightarrow\)2N⁺¹ .1

\(\rightarrow\)6N+5 +28e\(\rightarrow\)4N0 +2N+1 .3

Al\(\rightarrow\)Al+3 +3e _________.28

\(\rightarrow\)28Al+102HNO3\(\rightarrow\)28Al(NO3)3+6N2+3N2O+51H2O

2Fe⁺² \(\rightarrow\)2Fe⁺³ +2e .5

Mn⁺⁷ +5e\(\rightarrow\)Mn⁺² .2

\(\rightarrow\)10FeSO4+2KMnO4+2KHSO4\(\rightarrow\)5Fe2(SO4)3+2MnSO4+2K2SO4+H2O

4. (5x-2y)AL + (18x-6y)HNO3 -------> (5x-2y)AL(NO3)3 + 3NxOy +(9x-3y)H2O

5. 2M + 2nH2SO4--------> M2(SO4)n + nSO2 + 2nH2O

6. (5x-2y)M + (6nx-2ny)HNO3 -------->(5x-2y) M(NO3)n +n NxOy + (3nx-ny)H2O

7. 11Zn + 28HNO3 -------> 11Zn( NO3)2 + 2NO + 2N2O + 14H2O

8. 46AL + 168HNO3 -------;> 46AL( NO3)3 + 9N2 + 6N2O + 84H2O

9. 10FeSO4 + 2KMnO4 + 16KHSO4 ---> 5Fe2(SO4)3 +9 K2SO4 + 2MnSO4 + 8H2O.

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)

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

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

Đáp án : B

(3x + 8y)     Al -> Al³⁺ + 3e

3                 (x + 2y)N⁵⁺ + (3x + 8y) -> xN²⁺ + 2yN¹⁺ 

=> số phân tử HNO₃ bị khử = số N trong sản phẩm khử = 3(x + 2y) = 3x + 6y