I have a question in chemistry about combining compounds. I didn't really understand from my teacher. I have to combine Pb(NO3)2 with Na4OH. Also combine CaCl2 with Na2SO4. Can someone explain.

Answer 1

There is no Na4OH. I assume you meant NaOH although you may have meant NH4OH.
I think your teacher may be talking about solubility. Pb(NO)3 + NaOH produces Pb(OH)2 which is insoluble in aqueous solution. CaCl2 + Na2SO4 produces CaSO4 which is insoluble in aqueous solution. Here is a simplified list of solubility rules. http://www.chem.vt.edu/RVGS/ACT/notes/solubility_rules.html

Answer 2

thanks