Mg+H2SO4----->MgSO4+S+H2S+H2O ( nS : nH2S = 2 : 1) Cân bằng

Đáp án:

$1\times| 3\mathop{S}\limits^{+6}+ 20e\to 2\mathop{S}\limits^0+\mathop{S}\limits^{-2}$

$10\times| \mathop{Mg}\limits^0\to \mathop{Mg}\limits^{+2}+2e$ 

PTHH:

$10Mg+13H_2SO_4\to 10MgSO_4+2S+H_2S+ 12H_2O$