Question

Assertion: $N{{H}_{3}}$ is a lewis base
Reason: It can accept a proton
A. Both Assertion and Reason are true and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.
C. Assertion is true but Reason is false.
D. Assertion is false but reason is true.
E. Both Assertion and Reason are false.

Answer 1

Acids are generally those substances which are capable of donating a proton i.e. hydrogen atom to another substance while bases are those substances which are able to accept a hydrogen ion from an acid.

Complete answer:
Those compounds which have a high tendency to donate an electron pair always show high electron affinity. Those chemical species which have the ability to donate an electron pair to a given Lewis acid in order to form adducts are known as Lewis bases.
$N{{H}_{3}}$​ is said to be lewis base because it can donate an electron pair. But the reason given does not explain the assertion as it is not necessary that it will accept the proton represented by positive ions i.e. by ${{H}^{+}}$ only. A Lewis base can be defined as any species that donates a pair of electrons to a Lewis acid to form a Lewis adduct. For example $N{{H}_{3}}$ can act as lewis bases because they can donate a lone pair of electrons. In the adduct, the Lewis acid and base share an electron pair furnished by the Lewis base.

Hence option B is the correct answer.

Note:
Lewis bases are electron-rich species that we can say that they have the ability to donate electron-pairs and these are classified in the category of nucleophiles while Lewis acids are kept in the category of electrophiles.