Question

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R
Assertion A: The $H–O–H$ bond angle in water molecule is ${104.5}^o$
Reason R: The lone pair – lone pair repulsion of electrons is higher than the bond pair-bond pair repulsion.
In the light of the above statements, choose the correct Ans: from the options given below:

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

Answer 1

The correct option is C Both A and R are true, and R is the correct explanation of A

In water molecule, $O$ atom is $s{p}^3$ hybridised, hence the shape should have been tetrahedral if there were all bond pairs (bp) but two lone pairs (lp) are also present in $H_{2}O$. So the shape is distorted tetrahedral or angular. The reason is lone pair-lone pair(lp-lp) repulsion is more than lone pair-bond pair (lp-bp) repulsion which is more than bond pair bond pair (bp-bp) repulsion. Thus, the angle is reduced to ${104.5}^o$ from ${109.5}^o$.