To measure the quantity of MnCl _ 2 dissolved in an aqueous...

To measure the quantity of

{MnCl}_{2}

dissolved in an aqueous solution, it was completely converted to

{KMnO}_{4}

using the reaction,

{MnCl}_{2} + {K}_{2}{S}_{2}{O}_{8} + {H}_{2}O \to {KMnO}_{4} + {H}_{2}{SO}_{4} + HCl

(equation not balanced). Few drops of concentrated

HCl

were added to this solution and gently warmed. Further, oxalic acid \left(225mg\right)

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

{MnCl}_{2}

(in mg) present in the initial solution? (Atomic weights in

g{mol}^{- 1}: Mn = 55, Cl = 35 .5) To measure the quantity of MnCl _ 2 dissolved in an aqueous solution, it was completely converted to KMnO _ 4 using the

Correct answer

126

Step-by-step solution

{C}_{2}{O}_{4}^{- -} + {MNO}_{4}^{-}\overset{{H}^{+}}{\to}{CO}_{2}

{m}_{eq}of{C}_{2}{O}_{4}^{- -} = {m}_{eq}of{MNO}_{4}^{-}

2 \times \dfrac{0 .225}{90} = a \times 5 ⇒ a = 0 . 001mole = 1milimole

Massof{MnCl}_{2} = 1 \times \left[55 + 71\right]

<br >

= 126mg

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