Question

In the following question a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below.

Assertion(A): Though the central atom of both $N{H}_3\text{and}{H}_{2}O$ molecules are $s{p}^3$ hybridised, yet $H-N-H$ bond angle is greater than that of $H-O-H$.

Reason(R): This is because the nitrogen atom has one lone pair and oxygen atom has two lone pairs.

• A. A and R both are false.
• B. A is true but R is false.
• C. A and R both are correct, and R is the correct explanation of A.
• D. A and R both are correct, but R is not the correct explanation of A.

Answer 1

The correct option is C

A and R both are correct, and R is the correct explanation of A.

Analyzing assertion and reason

• The central atom $N\text{in the}N{H}_3$ molecule is surrounded by $4$ electron pairs ($3$ bond pairs $+1$1 lone pair). The hybridisation of the central atom is $s{p}^3$.
• The central atom $O\text{in the}{H}_{2}O$ molecule is surrounded by $4$ electron pairs ($2$ bond pairs $+2$ lone pairs). The hybridisation of the central atom is $s{p}^3$.

• But, the $H-N-H$ bond angle in $N{H}_3$ molecule is greater than the $H-O-H$ bond angle in $H_{2}O$ molecule because lone pair-lone pair repulsion in $H_{2}O$ molecule is greater than the lone pair-bond pair repulsion in $N{H}_3$ molecule which reduces the bond angle in water molecule