IC3

Question 1

Describe the flame test

Answer 1

1. Dip a nichrome wire loop in concentrated hydrochloric acid to clean it
2. Dip the nichrome loop into the unknown compound
3. Hold the loop in the clear blue part of a Bunsen burner flame and observe the colour change
4. Calcium ion = brick red flame
   Strontium ion = red flame
   Barium ion = pale green flame

Question 2

Describe the test for ammonium ions

Answer 2

1. Use a damp piece of red litmus paper
2. The paper will turn blue if ammonia is present
3. Add hydroxide ions to a solution containing ammonium ions. they will react to produce ammonia gas and water
4. Add some dilute sodium hydroxide solution to your mystery substance in a test tube and gently heat the mixture
5. If ammonia is given off, ammonium ions must be present

Question 3

Describe the test for sulfate ions

Answer 3

1. Add dilute hydrochloric acid
2. Add barium chloride
3. If white precipitate of barium sulfate forms, the original compound contained a sulfate

Question 4

Describe the test for hydroxide ions

Answer 4

1. Use a pH indicator e.g red litmus paper turns blue if hydroxide ions are present

Question 5

Describe the test for halide ions

Answer 5

1. Add dilute nitric acid to remove any ions which might interfere with the test
2. Add silver nitrate solution
3. Chloride = white precipitate
   Bromide = cream precipitate
   Iodide = yellow precipitate
4. Add ammonia solution
5. Silver chloride = dissolves in dilute ammonia solution
   Silver bromide = dissolves in concentrated ammonia solution
   Silver iodide = does not dissolve in concentrated ammonia solution

Question 6

Describe the test for carbonate ions

Answer 6

1. Add hydrochloric acid
2. Solution containing carbonate ions will fizz
3. Test for carbon dioxide using limewater
4. Limewater turns cloudy if carbon dioxide is present