Chapter 21, Problem 21.41P

Interpretation Introduction

Interpretation:

The balanced equation has to be written for the oxidation of p-xylene to 1,4-benzenedicarboxylic acid using potassium dichromate in aqueous sulfuric acid, and milligrams required of ${\text{H}}_{\text{2}}{\text{CrO}}_{\text{4}}$ is to be calculated.

Concept introduction:

To balance half-reactions in Acidic conditions:

Balance oxidation number with electrons

Balance elements except oxygen and hydrogen.

Balance oxygen with water.

Balance H with ${\text{H}}^{\text{+}}$ ion.

Balance net charge with electrons

Balance net equation with ${\text{OH}}^{\text{-}}$

Oxidation: Loss of electron

Reduction: Gain of electron

An oxidizing agent gains the electrons and is reduced in a chemical reaction and it is electron acceptor.

A reducing agent loses electrons and is oxidized in a chemical reaction and it is electron donor.

The oxidation state is called as oxidation number, which describes degree of oxidation (loss of electrons) of an atom in a chemical compound. Theoretically, the oxidation state is positive, negative or zero.