Test for Ions

Question 1

Describe flame tests used to identify group 2 ions

Answer 1

Dip a nichrome wire loop in concentrated hydrochloric acid.

Then dip the wire loop into the unknown compound.

Hold the loop in clear blue part of the Bunsen flame.

Observe colour change in the flame

Question 2

Colour of Calcium Ion in Flame Test

Answer 2

Brick-red

Question 3

Colour of Strontium Ion in Flame Test

Answer 3

Red

Question 4

Colour of Barium Ion in Flame Test

Answer 4

Pale green

Question 5

Describe using red litmus paper to test for ammonium ions

Answer 5

Ammonia gas is alkaline so can test for it using damp piece of red litmus paper.
Needs to be damp so ammonia gas can dissolve.

If ammonia’s present, the paper will turn blue (ie from red to blue)

Question 6

Describe using NaOH to test ammonia for ammonium ions

Answer 6

Add some dilute sodium hydroxide solution to a substance in a test tube and gently heat the mixture.

If ammonia’s given off, ammonium ions must be present

Question 7

Test for Sulfates with HCl and Barium Chloride

Answer 7

To identify a sulfate ion, add a little dilute hydrochloric acid, followed by barium chloride solution.

If a white precipitate of barium sulfate forms, it means the original compound contained a sulfate

Question 8

Using a pH indicator to test for hydroxides

Answer 8

Dip a piece of red litmus paper into the solution.

If hydroxide ions are present, the paper will turn blue

Question 9

Test for halides with silver nitrate solution

Results for:

Chloride

Bromide

Iodide

Answer 9

Add dilute nitric acid followed by silver nitrate solution.

White precipitate of silver chloride.

Cream precipitate of silver bromide.

Yellow precipitate of silver iodide

Question 10

Using hydrochloric acid to test for carbonates

Answer 10

By adding dilute hydrochloric acid, a solution containing carbonate ions will fizz.
(carbon ions react with the hydrogen ions in the acid to give carbon dioxide).

Test for CO2 using limewater. CO2 turns limewater cloudy- just bubble the gas through a test tube of limewater.

If the limewater goes cloudy, your solution contains carbonate ions