Question

Assertion: Baryta water becomes turbid on passing ${ CO }_{ 2 }$ gas through it but turbidity becomes clear on passing more ${ CO }_{ 2 }$ gas.
Reason: Carbonates give white precipitates with silver nitrate solution. The precipitate becomes yellow or brown if the mixture is boiled.
(a) Both Assertion and Reason are correct and Reason is the correct explanation for the Assertion.
(b) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
(c) Assertion is incorrect but the reason is correct.
(d) Both assertion and reason are correct.

Answer 1

Hint: For the assertion part, the chemical reactions will be very similar to that of the lime water test. The lime water test consists of passing the evolved gas through lime water which turns milky if the passed gas is carbon dioxide.

Complete step by step solution:
Lime water test is a popular test to check whether the evolved reaction is carbon dioxide gas or not. The test involves passing the evolved gas through lime water (aqueous solution of calcium hydroxide). If the gas is carbon dioxide, then we will observe that the lime water will turn milky which is due to the formation of calcium carbonate. The reaction is given below:
${ CO }_{ 2 }(g)+{ Ca(OH) }_{ 2 }(aq)\rightarrow { CaCO }_{ 3 }(s)\downarrow +{ H }_{ 2 }O(l)$
Baryta water is an aqueous solution of Barium hydroxide. It reacts with carbon dioxide and gives a white precipitate of barium carbonate. The formation of barium carbonate makes the solution turbid. The reaction is given below:
${ CO }_{ 2 }(g)+{ Ba(OH) }_{ 2 }(aq)\rightarrow { BaCO }_{ 3 }(s)\downarrow +{ H }_{ 2 }O(l)$
When the carbon dioxide gas is passed through Baryta water for a prolonged period of time then the initially formed precipitate of barium carbonate dissolves and the solution becomes clear. This is because the carbon dioxide reacts with barium carbonate to form barium bicarbonate which is soluble in water. The reaction is given below:
${ BaCO }_{ 3 }(s)+{ H }_{ 2 }O(l)+{ CO }_{ 2 }(g)\rightarrow { Ba(HCO }_{ 3 }{ ) }_{ 2 }(aq)$
When carbonates are reacted with a solution of silver nitrate, precipitation takes place. The precipitate formed is silver carbonate which is white in colour. The reaction is given below:
${ CO }_{ 3 }^{ 2- }(aq)+{ Ag }^{ + }(aq)\rightarrow { Ag }_{ 2 }{ CO }_{ 3 }(s)\downarrow (white\quad precipitate)$
If this mixture is boiled, we observe the formation of a yellow/brown precipitate of silver oxide. The reaction is shown below:
${ Ag }_{ 2 }{ CO }_{ 3 }(s)\xrightarrow { Boiled } { Ag }_{ 2 }{ O }_{ 3 }(s)\downarrow +{ CO }_{ 2 }(g)$
Therefore both the assertion and the reason are correct but the reason is not the correct explanation of the assertion.

Hence the correct answer is (b) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

Note: Just like the precipitate of barium carbonate dissolves on passing carbon dioxide for a prolonged period of time through the solution, similarly, the precipitate of calcium carbonate also dissolves on passing carbon dioxide for a prolonged time through lime water due to the formation of calcium bicarbonate