Select the correct n-factor(s) per formula unit of the species named, for the stated change.

A $KMnO X_{4}$ in acidic medium: $5$
B $K X_{2} Cr X_{2} O X_{7}$ in acidic medium ( $Cr X^{3 +}$ ): $6$
C $Na X_{2} S X_{2} O X_{3}$ oxidised by $I X_{2}$ to $Na X_{2} S X_{4} O X_{6}$ : $2$
D $H X_{2} O X_{2}$ acting as reductant ( $O X_{2}$ ): $2$

Answer: A, B, D

Thiosulfate:

2 S X_{2} O X_{3} X^{2 -} S X_{4} O X_{6} X^{2 -} + 2 e X^{-}

, so each formula unit loses only

1

electron and

n = 1

(option 3 is wrong). Permanganate

7 \to 2

gives

5

, dichromate

2 \times (6 \to 3) = 6

, and

H X_{2} O X_{2}

(two O atoms,

- 1 \to 0

) gives

2