Select the correct statement(s) about $n$ -factors (reduction to the stated product in the stated medium, oxidation to the stated product for reductants).

A $KMnO X_{4}$ reduced to $MnO X_{2}$ in neutral medium has $n = 3$
B $K X_{2} Cr X_{2} O X_{7}$ reduced to $Cr X^{3 +}$ in acidic medium has $n = 6$ per formula unit
C $H X_{2} C X_{2} O X_{4}$ oxidised to $CO X_{2}$ has $n = 1$
D $FeC X_{2} O X_{4}$ oxidised to $Fe X^{3 +}$ and $CO X_{2}$ has $n = 3$

Answer: A, B, D

Mn:

+ 7 \to + 4

gives 3, so A is true. Two Cr:

2 \times 3 = 6

, so B is true.

H X_{2} C X_{2} O X_{4}

: two C go

+ 3 \to + 4

, giving

n = 2

, so C is false.

FeC X_{2} O X_{4}

1 + 2 = 3

, so D is true.