Question

In neutral or faintly alkaline solution, 8 moles of permanganate anion quantitatively oxidize thisosulphate anions to produce X moles of a sulphur containing product. The magnitude of X is. ___

Answer 1

$Mn{O}_4^{-}+S_2{O}_3^{2-}\to M{n}^{4+}+S{O}_4^{2-}$

Key idea here is that since permanganate is a strong oxidising agent, we get $S{O}_4^{2-}$ as the product.
On balancing this, we get:
(change in O.N is 3 for $Mn$ in permanganate and 8 for 2 atoms of S)

$8Mn{O}_4^{-}+3S_2{O}_3^{2-}\to 8M{n}^{2+}+6S{O}_4^{2-}$

Just with this form of the equation we have the answer to be 6.