QJEEAdv18Ch2d4f: JEE Advanced 2018 Chemistry - Class 11 JEEAdv18Ch2d4f Solution: To measure the quantity of M n C l 2 dissolved in an aqueous…

Question

Verified Solution • 2025–26 Session moderate

To measure the quantity of

M n C l_{2}

dissolved in an aqueous solution, it was completely converted to

K M n O_{4}

using the reaction,

M n C l_{2} + K_{2} S_{2} O_{8} + H_{2} O \to K M n O_{4} + H_{2} S O_{4} + H C l

(equation not balanced).

Few drops of concentrated

H C l

were added to this solution and gently warmed. Further, oxalic acid (

225

m g

) was added in portions till the colour of the permanganate ion disappeared. The quantity of

M n C l_{2}

(in mg) present in the initial solution is ____________.

(Atomic weights in

g m o l^{- 1} : M n = 55, C l = 35.5

)

Accepted Answer

JEE Advanced 2018 Paper 2 Offline Chemistry - Some Basic Concepts of Chemistry Question 11 English Explanation

Also,

$2 M n O_{4}^{-} + 5 C_{2} O_{4}^{2 -} \to 2 M n^{2 +} + 10 C O_{2}$

Hence, $2 M n^{2 +} \equiv 5 C_{2} O_{4}^{2 -}$

$1 M n C l_{2} \equiv 2.5 H_{2} C_{2} O_{4}$

Oxalic acid taken = 225 mg

$= \frac{225}{90} = 2.5$ millimoles

Hence, MnCl₂ = 1 millimole

= (55 + 71) = 126 mg

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