Question

The reaction of sulphur in alkaline medium is given below:
$S_8\left(s\right)+aO{H}^{-}\left(aq\right)⟶b{S}^{2-}\left(aq\right)+c{S}_2{O}_3^{2-}\left(aq\right)+d{H}_{2}O\left(l\right)$

The value of a is (Integer answer)

Answer 1

$16e^{-}+S_8\to 8S^{2-}$

$12H_{2}O+S_8\to 4S_2{O}_3^{2-}+24H^{+}+16e^{-}$

$2S_8+12H_{2}O\to 8S^{2-}+4S_2{O}_3^{2-}+24H^{+}$

For balancing in basic medium add an equal number of $O{H}^{-}$ that of $H^{+}$

$2S_8+12H_{2}O+24O{H}^{-}\to 8S^{2-}+4S_2{O}_3^{2-}+24H_{2}O$

$2S_8+24O{H}^{-}\to 8S^{2-}+4S_2{O}_3^{2-}+12H_{2}O$

$S_8+12O{H}^{-}\to 4S^{2-}+2S_2{O}_3^{2-}+6H_{2}O$

$\therefore a=12$