Which of the following reactions are redox reactions? which of the following reactions are redox reactions? ca(s)+cl2(g)→cacl2(s) hcl(aq)+naoh(aq)→h2o(l)+nacl(aq) zn(s)+fe2+(aq)→zn2+(aq)+fe(s) ba(no3)2(aq)+k2so4(aq)→baso4(s)+2kn o3(aq)

Answer :  The redox reactions are:

Explanation :

Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.

(1)

This reaction is a redox reaction.

In this reaction, the oxidation state of 'Ca' changes from (0) to (+2) that means 'Ca' lost 2 electrons and it shows oxidation reaction and the oxidation state of 'Cl' changes from (0) to (-1) that means 'Cl' gain 1 electron and it shows reduction reaction.

(2)

This reaction is a double-displacement reaction in which the cation of two reactants molecule exchange their places to give two different products.

In double-displacement reaction, the oxidation state of cation and anion remains same on both side of the reaction. So, it is not a redox reaction.

(3)

This reaction is a redox reaction.

In this reaction, the oxidation state of 'Zn' changes from (0) to (+2) that means 'Zn' lost 2 electrons and it shows oxidation reaction and the oxidation state of 'Fe' changes from (+2) to (0) that means 'Fe' gain 2 electron and it shows reduction reaction.

(4)

This reaction is a double-displacement reaction in which the cation of two reactants molecule exchange their places to give two different products.

In double-displacement reaction, the oxidation state of cation and anion remains same on both side of the reaction. So, it is not a redox reaction.