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?

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.

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

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.

To determine whether the unknown is copper (II) nitrate or copper (II) sulfate, you can use a simple chemical test.

If you add sodium hydroxide (NaOH) to a solution containing copper (II) nitrate or copper (II) sulfate, you will observe the formation of a precipitate. Both copper (II) nitrate and copper (II) sulfate will react with NaOH to form copper (II) hydroxide, which is insoluble and appears as a solid precipitate.

Therefore, adding NaOH alone as a test reagent will not distinguish between copper (II) nitrate and copper (II) sulfate since they both produce the same reaction.

To differentiate between the two possibilities, you can perform an additional test using a different reagent. One possible test involves the use of ammonium hydroxide (NH4OH).

When you add ammonium hydroxide to a solution containing copper (II) nitrate, it will form a deep blue solution due to the formation of a complex ion known as tetraamminecopper (II) complex: [Cu(NH3)4]2+. This complex has an intense blue color.

However, when you add ammonium hydroxide to a solution containing copper (II) sulfate, it will just form a pale blue precipitate of copper (II) hydroxide, similar to the reaction with NaOH.

By performing the additional test with ammonium hydroxide, you can observe the color change in the solution. If it turns deep blue, then your unknown is likely copper (II) nitrate. If it forms a pale blue precipitate, then your unknown is likely copper (II) sulfate.

Remember, it's always important to use caution when working with chemicals and perform tests in a well-ventilated area. Additionally, following proper laboratory safety protocols and guidelines is crucial.