Question

Assertion :Melting and boiling points of $D_{2}O$ are higher than those of ordinary $H_{2}O$. Reason: $D_{2}O$ has lesser degree of association and lower molecular mass than $H_{2}O.$

• 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 C Assertion is correct but Reason is incorrect

$D_{2}O$ has higher molecular mass and a greater degree of association than and $H_{2}O$ and thus has higher melting and boiling points.

Note: Molecular mass of $H_{2}O=2\left(1\right)+16=18$. Molecular mass of $D_{2}O=2\left(2\right)+16=20$.