Question

Enter a balanced equation for the reaction of Na2S and CdSO4.

Answer 1

This type of a reaction is a double displacement reaction. where the reactants displace each other. the cations and the anions the reactant compounds replace each other or in other words switch places. the anion of one compound will bond with the cation of the other compound and vice versa.

the equation for the above is 
Na₂S + CdSO₄ ---> CdS + Na₂SO₄
the numbers of atoms on both sides are balanced now 

Answer 2

Answer:  $Na_2S+CdSO_4\rightarrow Cd_2S+Na_2SO_4$

Explanation:

According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

Double displacement reaction is one in which exchange of ions take place.

The balanced chemical reaction will be:

$Na_2S+CdSO_4\rightarrow Cd_2S+Na_2SO_4$