Acidified $0.1$ mol $Fe X^{2 +}$ is oxidised to $Fe X^{3 +}$ . Select the oxidant amount(s) that react exactly completely with it ( $MnO X_{4} X^{-} Mn X^{2 +}$ , $Cr X_{2} O X_{7} X^{2 -} Cr X^{3 +}$ , $H X_{2} O X_{2} H X_{2} O$ ).

Answer: A, B

Equivalents of

Fe X^{2 +} = 0.1

KMnO X_{4}

(

n = 5

0.1/5 = 0.02

mol (A true).

K X_{2} Cr X_{2} O X_{7}

(

n = 6

0.1/6 = 0.0167

mol (B true; D false).

H X_{2} O X_{2}

(

n = 2

0.05

mol, so C (0.10 mol) is false.