Determine if precipitation occurs and write the proper ionic equation

Question

a) Na2O3+NiCL2
b) Pb(NO3)2+ALCL3

Answer 1

Whether a ppt forms or not depends upon the concentrations; i.e., the solublity product must be exceeded.

In general, however, what you want is
Ni^2+(aq) + CO3^2-(aq) ==> NiCO3(s)
3Pb^2+(aq) + 6Cl^-(aq) ==> 3PbCl2(s)