Question

Balance cr2o7 2- + so2----cr3+ + so4 2- in acid medium

Answer 1

Step 1. Write down the unbalanced equation ('skeleton equation') of the chemical reaction. All reactants and products must be known. For a better result write the reaction in ionic form.

 

SO32- + Cr2O72- → Cr3+ + SO42-

 

Step 2. Separate the redox reaction into half-reactions. A redox reaction is nothing but both oxidation and reduction reactions taking place simultaneously.

a) Assign oxidation numbers for each atom in the equation. Oxidation number (also called oxidation state) is a measure of the degree of oxidation of an atom in a substance (see: Rules for assigning oxidation numbers).

 

S+4O-232- + Cr+62O-272- → Cr+33+ + S+6O-242-