20mL of 0 . 02M hypo solution is used for the titration of 10mL of...

$20mL$ of $0 . 02M$ hypo solution is used for the titration of $10mL$ of copper sulphate solution, in the presence of excess of $KI$ using starch as an indicator. The molarity of ${Cu}^{2 +}$ is found to be $_____ \times {10}^{- 2}M$ (nearest integer)

Given : $2{Cu}^{2 +} + 4{I}^{-} \to {Cu}_{2}{I}_{2} + {I}_{2}{I}_{2} + 2{S}_{2}{O}_{3}^{- 2} \to 2{I}^{—} + {S}_{4}{O}_{6}^{- 2}$

Correct answer

Step-by-step solution

{n}_{eq .} of {I}_{2} = {n}_{eq} of ${Na}_{2}{S}_{2}{O}_{3} = 20 \times 0 . 02 \times {10}^{- 3}$
$2 \times {n}_{mol}$ of ${I}_{2} = 0 . 4 \times {10}^{- 3}$
${n}_{mol} of {I}_{2} = 0 . 2mmol$
{n}_{mol} of ${Cu}^{+ 2} = 0 . 2 \times 2 \times {10}^{- 3}$
\left[{Cu}^{+ 2}\right] = \dfrac{0 . 4 \times {10}^{- 3}}{10 \times {10}^{- 3}} = 0 . 04 = 4 \times {10}^{- 2}

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