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A student was given samples of the following salts: sodium sulfate (Na2SO4), sodium sulfite (Na2SO3), potassium sulfate (K2SO4) - Leaving Cert Chemistry - Question e - 2003
Question e
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... show full transcript
Worked Solution & Example Answer:A student was given samples of the following salts: sodium sulfate (Na2SO4), sodium sulfite (Na2SO3), potassium sulfate (K2SO4) - Leaving Cert Chemistry - Question e - 2003
Step 1
What test could be carried out to distinguish between the sodium salts and the potassium salt?
Answer
To distinguish between sodium sulfate and potassium sulfate, a flame test can be conducted. In this test, a small amount of each salt is placed in a flame and the colors of the flame are observed. Sodium will produce a bright yellow-orange flame, while potassium will yield a lilac or violet flame, although it is important to note that it should not appear purple.
Step 2
What observation would you make in this test?
Answer
Upon conducting the flame test, the following observations are made: the sodium salt (either sulfate or sulfite) will produce a yellow/orange flame, and the potassium salt will display a lilac flame. This color differentiation allows for the identification of each salt.
Step 3
Describe the test which could be carried out to distinguish between the sulfite salts and the sulfate salt.
Answer
To distinguish between sodium sulfite (Na2SO3) and sodium sulfate (Na2SO4), barium chloride (BaCl2) can be used. When a solution containing either sulfite or sulfate is treated with barium chloride, a white precipitate will form if sulfate ions are present. The test will proceed as follows:
- Add dilute hydrochloric acid (HCl) to the mixture of the salt solution and barium chloride.
- If sodium sulfite is present, the precipitate will dissolve in the acid, indicating the presence of sulfite ions.
- However, if sodium sulfate is present, the white precipitate created will remain intact, indicating the presence of sulfate ions.
The distinction lies in the solubility of the precipitate: sulfate salts yield a non-dissolving precipitate, while sulfite salts produce one that dissolves upon acidification.