Question

Redox Reactions

1) What distinguishes a redox reaction from a chemical reaction such as a double replacement?

2) COnsider the following unbalanced net ionic redox equation.

VO₂⁺+SO₃^2- -> VO⁺+SO₄^2-

a) Name the oxidizing agent in this reaction.

b) Name the ion that is oxidized in this reaction.

c) Balance this net ionic redox equation in acidic solution.

Answer 1

(1) In a redox reaction the chemical change is accompanied by transfer of electrons while in a non-redox reaction there is no transfer of electrons.

In redox reactions (oxidation-reduction reactions) a change in the oxidation number occurs. Elements that are reduced gain electrons, and elements that are oxidized lose electrons.

There are several types of non redox reactions, including decomposition, combination, single displacement, and double displacement.

Lets define double displacement or double replacement briefly
.AB + CD CB + AD

Cations and anions switch their positions. No transfer of electrons taking place.

2). VO₂⁺+ SO₃^2- VO⁺+ SO₄^2-

Reduction half reaction: VO₂⁺ VO⁺ (V is in +5 oxidation state in VO₂⁺ and in +3 oxidation state in VO⁺. Gain of two electrons.)

Oxidation half reaction: SO₃^2- SO₄^2- (S is in +4 oxidation state in SO₃^2- and in +6 oxidation state in SO₄^2- . Loss of two electrons)

(a) An oxidising agent in a reaction is the species which gains electrons and gets reduced in the reaction. Therefore VO₂⁺ is the oxidising agent.

(b) SO₃^2- ion is getting oxidised by loosing 2 electrons.

(c) In acidic solution we balance the reaction by using H+ ions and H₂O

Reduction Half reaction: VO₂⁺ + 2H⁺ + 2e- VO⁺ + H₂O

Oxidation half reaction: SO₃^2- + H₂O SO₄^2- + 2H⁺ + 2e-

Balanced reaction: VO₂⁺+ SO₃^2- VO⁺+ SO₄^2-