Tests for cations

Question 1

What is the flame test procedure?

Answer 1

1) Clean a platinum wire loop by dipping it in some dilute hydrochloric acid and then holding it over a blue Bunsen burner flame.
2) Dip the loop into the sample you want to test and put it back in the flame.
3) Record the colour of the flame

Question 2

What is the colour of each metal ion flame?

Answer 2

Lithium ions burn with a crimson flame.
Sodium ions burn with a yellow flame.
Potassium ions burn with a lilac flame.
Calcium ions burn with an orange-red flame.
Copper ions burn with a green flame.

Question 3

What happens if a sample tested in a flame test contains a mixture of metal ions?

Answer 3

Some flame colours may be hidden.

Question 4

What is the metal hydroxide test?

Answer 4

Add a few drops of sodium hydroxide solution to a solution of your mystery compound and see what colour the solution turns.

Question 5

What is the colour of each metal ion in a metal hydroxide test?

Answer 5

Calcium forms a white precipitate.
Copper (II) forms a blue precipitate.
Iron (II) forms a green precipitate.
Iron (III) forms a brown precipitate.
Aluminium forms a white precipitate at first but redissolves in excess NaOH to form a colourless solution.
Magnesium forms a white precipitate.