Ncert Exercises & Solutions

Given below are two statements:

Assertion (A):	Among the two O-H bonds in H₂O molecule, the energy required to break the first O-H bond and the other O-H bond is the same.
Reason (R):	The electronic environment around oxygen is the same even after the breakage of one O-H bond.

1.	Both (A) and (R) are True and (R) is the correct explanation of (A).
2.	Both (A) and (R) are True but (R) is not the correct explanation of (A).
3.	(A) is True but (R) is False.
4.	Both (A) and (R) are False.

Hint: \(^-O-H\) is formed after one \(O-H\) breakage in water molecule.

Explanation:

A covalent bond is present in a water molecule because one oxygen atom shares its two electrons with two hydrogen atoms.

The energy required to break the first bond is not the same as that of the second bond in a water molecule, which means the bond enthalpies of the two are different. After the breakage of one \(O-H\)bond.

The electronic environment around the oxygen atom in water molecules is not the same even after the bond breaks. The electron density in \(OH^-\) is more than \(H_2O\). So, the bond enthalpies will be different.

So, both assertion and reason are false. Option 4 is the correct answer.

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