Chemical tests

Stage 1

Identify the unknown gas, anion or cation in the following tests.

1. Give the name and formula (including charge) of the ion that gives a white precipitate when sodium hydroxide solution is added, and redissolves when excess sodium hydroxide solution is added.

2. Give the name and formula (including charge) of the ion that fizzes and gives off carbon dioxide when a dilute acid is added.

3. Give the name and formula (including charge) of the ion that gives a white precipitate when acidified silver nitrate is added.

4. Give the name and formulae (including charges) of the two ions that give a white precipitate when sodium hydroxide solution is added but do NOT redissolve when excess sodium hydroxide solution is added.

5. Which gas relights a glowing splint?

Stage 2

6. Identify the unknown compound from the following chemical tests:

  • A green precipitate was produced when aqueous sodium hydroxide was added.
  • Gave a cream precipitate when acidified silver nitrate was added.

7. Identify the unknown compound from the following chemical tests:

  • A flame test gave a yellow flame.
  • Gave a white precipitate when acidified barium chloride was added.

8. Identify the unknown compound from the following chemical tests:

  • A flame test gave a green flame.
  • Gave a white precipitate when acidified silver nitrate was added.

9. Identify the unknown compound from the following chemical tests:

  • A flame test gave a yellow flame.
  • Gave a white precipitate when acidified silver nitrate was added.

10. Identify the unknown compound from the following chemical tests:

  • A blue precipitate was produced when aqueous sodium hydroxide was added.
  • Gave a white precipitate when acidified silver nitrate was added.

Stage 1

1. aluminium(III), Al3+

2. carbonate, CO32-

3. chloride, Cl-

4. magnesium and calcium, Mg2+ and Ca2+

5. oxygen

Stage 2

6. iron(II)bromide

7. sodium sulfate

8. copper(II)chloride

9. sodium chloride

10. copper(II)chloride