Question

Assertion: The boiling point of $H_{2}O$ is higher than the boiling point of $H_{2}S$.
Reason: $H_{2}S$ has a greater molecular mass than $H_{2}O$.

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

Answer 1

The correct option is B

Both Assertion and Reason are correct and Reason is not the correct explanation of Assertion

Water $\left(H_{2}O\right)$ has hydrogen bonding and London forces. Hydrogen sulfide $\left(H_{2}S\right)$ has only London forces. The reason why water has hydrogen bonding and hydrogen sulfide does not is because the oxygen in water is more electronegative than the sulfur in hydrogen sulfide. Hydrogen bonding only occurs between molecules that have hydrogen bonded to a very electronegative atom, which is either oxygen, fluorine, or nitrogen.
A hydrogen bond is a intermolecular attraction between the hydrogen of one atom and the lone pair of electrons of another atom. In order for the bond to exist the lone pair of electrons must belong to a electronegative atom, so there will be a great tendency for attraction.
$\left(H_{2}O\right)$ is very strongly hydrogen bonded. These bonds require energy to break resulting in a higher boiling point.
Thus, both assertion and reason are correct and reason is not the correct explanation of assertion.