Question

Assertion: Concentrated ${H_2}S{O_4}$ cannot be used to prepare pure $HBr$ from $NaBr$.
Reason: it reacts slowly with $NaBr$
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

This question gives the knowledge about the oxidizing and reducing agents. Reducing agents are the chemical agents which reduce the other compounds and get oxidized itself. Oxidizing agents are the chemical agents which oxidizes the other compounds and reduces itself. $HBr$ is a very strong reducing agent.

Complete step-by-step answer: Reducing agents are the chemical agents which reduce the other compounds and get oxidized itself. Oxidizing agents are the chemical agents which oxidizes the other compounds and reduces themselves.

According to the question, the concentrated sulphuric acid is not useful in producing hydrogen bromide from sodium bromide. This means when $NaBr$ and ${H_2}S{O_4}$ reacts with each other they do not produce $HBr$. The reaction for this is as follows:

$NaBr + {H_2}S{O_4} \to HBr + NaHS{O_4}$

This reaction is wrong. To produce hydrogen bromide, $NaBr$ needs to be reacted with phosphoric acid. Also $HBr$ is a very strong reducing agent. As we know, Reducing agents are the chemical agents which reduce the other compounds and get oxidized itself. So, it oxidizes itself to bromine and generally reduces ${H_2}S{O_4}$ to sulphuric dioxide. The reaction for this is as follows:
$2HBr + {H_2}S{O_4} \to B{r_2} + S{O_2} + 2{H_2}O$
Therefore, it is proved that Concentrated ${H_2}S{O_4}$ cannot be used to prepare pure $HBr$ from $NaBr$. But this is not the valid reason that it reacts slowly with sodium bromide. So, Assertion is correct but Reason is incorrect.

Hence, option $3$ is the correct option.

Note: Reducing agents are the agents that possess very high oxidation states whereas the oxidizing agents are the agents that possess very low oxidation states. Oxidizing agents have the ability to accept the electrons from other molecules and reducing agents have the ability to donate the electrons to other molecules.