In neutral medium $Mn X^{2 +}$ is estimated by permanganate: $3 Mn X^{2 +} + 2 MnO X_{4} X^{-} + 2 H X_{2} O 5 MnO X_{2} + 4 H X^{+}$ . A 25.0 mL sample of a manganese(II) solution needs 12.4 mL of 0.0200 M $KMnO X_{4}$ . Find the concentration of Mn in mg per litre (Mn = 55), to the nearest integer.

Numerical answer type, answer in mg/L, tolerance 1.

Answer: 818 mg/L

mmol

MnO X_{4} X^{-}

12.4 \times 0.0200 = 0.248

. From the equation,

Mn X^{2 +}

0.248 \times 3/2 = 0.372

mmol in 25.0 mL, i.e. 0.01488 M. Mass concentration =

0.01488 \times 55 \times 1000

= 818.4 mg/L.