Redox reactions are the chemical reactions in which reduction and oxidation occurs

simultaneously. In straight words addition of oxygen is oxidation and removal of

hydrogen is reduction.

ELECTRONIC CONCEPT OF OXIDATION AND REDUCTION

Oxidation is a process in which an atom or an ion loses one or more electrons.

Reduction is a process in which an atom or an ion gains one or more electrons.

REDOX REACTION

Redox reactions may be regarded as electron transfer reactions in which the electrons

are transferred from one reactant to the other. As the result substance which losses

electrons is called a reducing agent or reductant while another which accepts the

electrons is called an oxidizing agent or oxidant.

REDOX REACTIONS IN AQUEOUS SOLUTION

In aqueous solutions, the spontaneous redox reactions can be carried out directly

as well as indirectly.

Direct Redox Reactions: Redox reactions in which oxidation and reduction takes

place in the same vessel are called direct redox reactions. In such reactions, the

transfer of electrons from reductant to oxidant occurs over a very short distance

(within molecular diameters). For example, if a zinc rod is placed in a solution of

copper sulphate in a beaker, a spontaneous reaction occurs and following changes

will be observed.

Observations for redox reaction occurring in a beaker

Zinc rod starts dissolving and loses its mass gradually.

The blue color of the solution starts fading.

Copper metal either starts settling at the bottom of the beaker or depositing on the

zinc rod.

The reaction is exothermic i.e., it takes place with the evolution of heat.

The solution remains electrically neutral throughout.

The reaction will not continue indefinitely but stops after some time.