JEE Main · 2021 · 27 Aug 2021 · Shift 1 · Redox Reactions and Electrochemistry

When 10 mL of an aqueous solution of

KMnO X_{4}

was titrated in acidic medium, equal volume of 0.1 M of an aqueous solution of ferrous sulphate was required for complete discharge of colour. The strength of

KMnO X_{4}

in grams per litre is ______

\times 1 0^{- 2}

. (Nearest integer)
[Atomic mass of

K = 39

Mn = 55

O = 16

]

Answer: 316

Solution

In acid the reaction is

Mn O_{4}^{-} + 8 H^{+} + 5F e^{2 +} \to M n^{2 +} + 5F e^{3 +} + 4 H_{2} O

, so the n-factors are

5

for

KMn O_{4}

and

1

for

FeS O_{4}

. Equal volumes reach the decolourising end point, so

5 \times M = 1 \times 0.1

, giving

M = 0.02 M

. With molar mass

39 + 55 + 4 (16) = 158 g mo l^{- 1}

, the strength is

0.02 \times 158 = 3.16 g L^{- 1}

, that is

316 \times 1 0^{- 2} g L^{- 1}

JEE Main · 2021 · 27 Aug 2021 · Shift 1 · Integer answer

Practise more: all JEE Main PYQs on Redox Reactions and Electrochemistry →

JEE Main · 2021 · 27 Aug 2021 · Shift 1 · Redox Reactions and Electrochemistry

Solution

More JEE Main questions on Redox Reactions and Electrochemistry