Question

Balance the reaction by both (oxidation number and half reduction equation) methods. S₂O₃²⁻ + Br₂ --> S₄O₆²⁻ + Br⁻

Answer 1

Basic equation  of the chemical reaction is written. All reactants and products must be known.

Then  write the reaction in ionic form.SO + Br → SO + Br...Separation of the reaction  into half reactions. 

:A redox reaction is nothing but both oxidation and reduction reactions taking place together.oxidation numbers should be assigned for each atom in the equation.

Oxidation number  is a measure of the degree of oxidation of an atom in a substance.S+2O-2 + Br0 → S+2O-2 + Br.

Answer 2

law of conservation of masses