Suppose you suspect that your unknown is either copper (II) nitrate or copper (II) sulfate. You decide to add NaOH to your known as a test reagent. Will this test distinguish between the two possibilities? If not, could you suggest a different test?

Answer 1

It will not distinguish since both will produce Cu(OH)2.
A better test is to add BaCl2. That will ppt a while ppt of BaSO4 with the sulfate but not the nitrate.

Answer 2

What if I had to use barium nitrate as the test reagent, how would each one react to that?

Answer 3

It's the Ba ion that does the job so as long as the salt is soluble, Ba anything (BaCl2, Ba(NO3)2, etc) will work.