Chemical Analysis- Hydroxide Precipitates

Question 1

How do you perform a hydroxide precipitate test?

Answer 1

Dissolve a small quantity of the substance in water.
Place about 5cm3 of the solution into a test tube.
Add a few drops of sodium hydroxide solution.
Record the colour of any precipitate that’s formed.
Add dilute sodium hydroxide solution until it is in excess and record the result.

Question 2

What colour is the hydroxide precipitate of iron(II) and does it dissolve in excess sodium hydroxide?

Answer 2

Green, no

Question 3

What colour is the hydroxide precipitate of iron(III) and does it dissolve in excess sodium hydroxide?

Answer 3

Orange-Brown, no

Question 4

What colour is the hydroxide precipitate of copper(II) and does it dissolve in excess sodium hydroxide?

Answer 4

Blue, yes it becomes a deep blue.

Question 5

What colour is the hydroxide precipitate of calcium and does it dissolve in excess sodium hydroxide?

Answer 5

White, no

Question 6

What colour is the hydroxide precipitate of Zinc and does it dissolve in excess sodium hydroxide?

Answer 6

White, yes it becomes colourless.