A student was given samples of the following salts: sodium sulfate (Na2SO4) sodium sulfite (Na2SO3) potassium sulfate (K2SO4) (i) What test could be carried out to distinguish between the sodium salts and the potassium salt? (ii) What observation would you make in this test? (ii) Describe the test which could be carried out to distinguish between the sulfite salts and the sulfate salt. - Leaving Cert Chemistry - Question c - 2003

During the flame test:

• The sodium salt (either sodium sulfate or sodium sulfite) would manifest a yellow/orange flame, which is characteristic of sodium ions.
• The potassium salt would display a lilac/violet flame, indicative of potassium ions.

This distinct color difference is critical for differentiating between the sodium and potassium salts.

To distinguish between sulfite (Na2SO3) and sulfate (Na2SO4) salts, perform the following test:

1. Add barium chloride (BaCl2) or barium nitrate (Ba(NO3)2) solution to the test solution containing the sulfite or sulfate salt.
2. Observe the formation of a white precipitate, which indicates the presence of sulfate or sulfite ions.

• If the precipitate forms and does not dissolve upon the addition of dilute hydrochloric acid (HCl), this indicates the presence of sulfate ions.
• Conversely, if the precipitate dissolves when HCl is added, sulfite ions are present.

These observations confirm the identities of the salts based on their reactions with barium ions and hydrochloric acid.