Question

Write a formula for the compound that forms from barium and the following polyatomic ion.

(a) hydroxide

(b) carbonate

(c) phosphate

(d) hydrogen phosphate

basicaly all i know is that all of these are going to start with Na.

I need major help! thanks:)

Answer 1

If I interpret the question correctly, the question asks for Ba + each of the anions. I don't know where Na fits in. Perhaps there is more to the question than you posted.
Ba(OH)2
BaCO3
Ba3(PO4)2
BaHPO4

Answer 2

I get the first 2 but how did u get the second two?