Question

Assertion: Addition of $N{{H}_{4}}OH$ to an aqueous solution of $BaC{{l}_{2}}$ in the presence of excess $N{{H}_{4}}Cl$ precipitates $Ba{{\left( OH \right)}_{2}}$ .
Reason: $Ba{{\left( OH \right)}_{2}}$ is soluble in water.
(A) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(B) Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
(C) Assertion is correct but Reason is not correct.
(D) Assertion is not correct but Reason is correct.
(E) Both Assertion and Reason are not correct.

Answer 1

There is a possibility of having any one of the options to be correct as the question is based on the statements and the reasons. We need to see that for the given assertion, the reason is valid and also both of them are correct; or vice versa.

Complete Solution :
Let us see both the Assertion and Reason one by one;
- Assertion: Addition of $N{{H}_{4}}OH$ to an aqueous solution of $BaC{{l}_{2}}$ in the presence of excess $N{{H}_{4}}Cl$ precipitates $Ba{{\left( OH \right)}_{2}}$ .
- The above given statement says that when we add $N{{H}_{4}}OH$ to aqueous solution of $BaC{{l}_{2}}$ in the presence of excess of $N{{H}_{4}}Cl$, it gives the precipitate of $Ba{{\left( OH \right)}_{2}}$ which is false.
- Presence of excess of $N{{H}_{4}}Cl$ suppresses the dissociation of $N{{H}_{4}}OH$, which eventually reduces the concentration of $O{{H}^{-}}$ ions. Thus, when $N{{H}_{4}}OH$ is added to an aqueous solution of $BaC{{l}_{2}}$, precipitation of $Ba{{\left( OH \right)}_{2}}$ does not take place.

- Now, further
Reason: $Ba{{\left( OH \right)}_{2}}$ is soluble in water.
The above given statement says that $Ba{{\left( OH \right)}_{2}}$ is soluble in water; which is true.
So, the correct answer is “Option D”.

Note: he options (A) and (B) can never be correct as Assertion is incorrect and the Reason is correct. Thus, though reason is correct, it cannot explain the incorrect statement.