Question

Assertion: $Zn(s) + CuS{O_4}(aq) \to ZnS{O_4}(aq) + Cu(s)$
Zn is a reductant but itself gets oxidised.
Reason: In a redox reaction, oxidant is reduced by accepting electrons and reductant is oxidised by losing electrons.
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

Hint: A redox reaction is in which both oxidation and reduction occurs. Oxidation is a process of loss of electrons or increase in oxidation state. Gain of electrons or decrease in oxidation state is called reduction. A reaction which involves both oxidation and reduction is called a redox reaction.

Complete step by step answer:
The given reaction is,
$Zn(s) + CuS{O_4}(aq) \to ZnS{O_4}(aq) + Cu(s)$
In this reaction, the oxidation state of Zn is zero in reactants and $ + 2$ in products. Since the oxidation state of zinc increases in the reaction zinc is oxidised. Similarly, the oxidation state of Cu is $ + 2$ in reactants and zero in products. Since the oxidation state of Cu decreases in the reaction Cu is reduced.
The species which reduces the other substance is called reducing agent or reductant. They themselves get oxidised in the reaction. Similarly the species which oxidise the other substance is called oxidising agent or oxidant. They themselves get reduced in the reaction. In other words the reductant reduces the oxidant and oxidant oxidise the reductant. The electrons which are lost by the reductant will be accepted by oxidant and they get reduced.
Here Zn is oxidised. It reduces $C{u^{2 + }}$ to Cu. Hence Zn is the reductant. Hence the assertion is correct.
The oxidant is $C{u^{2 + }}$. It is reduced by accepting electrons from Zn and reductant (Zn) is oxidised by losing electrons to $C{u^{2 + }}$. Hence the reason, “In a redox reaction, oxidant is reduced by accepting electrons and reductant is oxidised by losing electrons” is also correct. As we have already seen, the reason is a correct explanation for the assertion.
Hence the correct option is A.

Note:
The above redox reactions can be broken down to oxidation half reaction containing only Zn and reduction half reaction containing only Cu. When doing this, the charge and number of electrons should also be balanced besides the number of atoms.