Question

Assertion :If $x$ mL of $0.1M$ $KMn{O}_4$ solutions requires $100$ mL of $0.1M$ $CuS$ solution for complete neutralization, then $x$ mL of same $KMn{O}_4$ solution would require $75$ mL of $0.1M$ $C{u}_{2}S$ solution. Reason: ${}^{\prime }{n}^{\prime }$ factor for $CuS$ and $C{u}_{2}S$ are $6$ and $8$ respectively .

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Both assertion and reason are correct and reason is the correct explanation of assertion.
Here is the explanation:
i. mEq. of $Mn{O}_4^{⊝}\equiv$ mEq. of $CuS$
$(n=5)$ $(n=6)(S^{2-}\to S{O}_2+6e^{-})$
$(C{u}^{2+}\to$ no change)
$x\times 0.1\times 5\equiv 100\times 0.1\times 6$
Therefore, $x=120$ mL.
ii. mEq. of $Mn{O}_4^{⊝}\equiv$ mEq. of $C{u}_{2}S$
$(n=5)$ $(n=8)(S^{2-}\to S{O}_2+6e^{-})$
$(2C{u}^{1+}\to 2C{u}^{2+}+2e^{-})$
$x\times 0.1\times 5\equiv 75\times 0.1\times 8$
Therefore, $x=120$ mL.