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Given below are two statements one is labelled as Assertion A  and the other is labelled as Reason R:

Assertion A: The amphoteric nature of water is explained by using Lewis acid/base concept.

Reason R: Water acts as an acid with \mathrm{NH_{3}} and as a base with \mathrm{H_{2}S}

In the light of the above statements choose the correct answer from the options given below:

Option: 1

Both A and are true and R is the correct explanation of A.


Option: 2

Both A and R are true but R is NOT the correct explanation of A.


Option: 3

A is true but R is false.


Option: 4

A is false but R is true


Answers (1)

best_answer

Water has the ability to act as an acid as well as a base, it behaves as an amphoteric substance. In the Bronsted sense , it acts as an acid with \text{NH}_{3} and a base with \text{H}_{2}\text{S}.

\begin{aligned} \mathrm{H}_{2} \mathrm{O}( {\ell})+\mathrm{NH}_{3}(\text { aq }) & \rightleftharpoons \mathrm{OH}^{\ominus }_{\text {(aq) }}+\mathrm{NH}_{4}^{\oplus } \text {(aq)} \end{aligned}

    \mathrm{acid}              \mathrm{Base}                \mathrm{CB}               \mathrm{CA}

\begin{aligned} \mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{H_{2}S}(\text { aq }) & \rightleftharpoons \mathrm{H_{3}O}^{\oplus }_{\text {(aq) }}+\mathrm{HSO}_{4}^{\ominus } \text { (aq) } \end{aligned}

\mathrm{Base}             \mathrm{Acid}                  \mathrm{CA}                 \mathrm{CB}

A is false, as the Amphoteric nature cannot be explained by using Lewis acid/base concept. It is explained by the Bronsted Lowry theory of acid and base

R is true.

Hence, the correct answer is Option (4)

Posted by

HARSH KANKARIA

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