Question

Assertion: On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears.
Reason: $BaS{O_3}$ is a salt of weak acid $\left( {{H_2}S{O_3}} \right)$, therefore dilute acid such as HCl decomposes barium sulphate to produce sulphur dioxide gas which has the smell of burning sulphur.
A.Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B.Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C.Assertion is correct but Reason is incorrect
D.Both Assertion and Reason are incorrect

Answer 1

The name of the compound $BaS{O_3}$ is barium sulfate. Barium sulfate is a white powder used in paper manufacturing. Most of the barium compounds are toxic which includes barium sulfate too.

Complete answer:
Barium sulfate is a white precipitate. The reaction which takes place between barium sulfite and hydrochloric acid is as follows,
$BaS{O_3} + 2HCl \to BaC{l_2} + S{O_2} + {H_2}O$
where $BaS{O_3}$ is barium sulfate, HCl is hydrochloric acid, $BaC{l_2}$ is barium chloride, $S{O_2}$ is sulphur dioxide and ${H_2}O$ is water.
Barium sulfate can also be prepared by the reaction of barium with sulphurous acid. Barium sulfide decomposes on the addition of hydrochloric acid. It decomposes and forms barium chloride and sulphur dioxide gas is released and water is produced too. So, the barium chloride obtained is soluble and hence white precipitate disappears. Hence the assertion, which states that on adding dilute hydrochloric acid to the reaction mixture, white ppt disappears; is true. Also, the reason that barium sulfide decomposes by hydrochloric acid to produce sulphur dioxide gas which has the smell of burning sulphur; is also true.
Therefore, the correct answer is that both assertion and reason are correct and the reason is the correct explanation for assertion.

Therefore, the correct option is A.

Note:
Barium chloride imparts yellow-green colouration to the flame and also it is toxic. Barium is an alkaline earth metal and is highly reactive and is thus never found in free form.