$\rm \mathop{S}\limits^{+4} \to \mathop{S}\limits^{+6}  +2e$

$\rm \mathop{Mn}\limits^{+7}+5e \to \mathop{Mn}\limits^{+2}  $

$n_{SO_2}=\dfrac{5.6}{22.4}=\dfrac{5.6}{22.4}=0.25(mol)$

Bảo toàn $e:$

$2n_{SO_2}=5n_{KMnO_4}$

`=>`$n_{KMnO_4}=0.25 \times \dfrac{2}{5}=0.1(mol)$

$V_{dd}=\dfrac{n}{C_M}=\dfrac{0.1}{2}=0.05(L)$