3.1.4 Qualitative analysis

Question 1

Describe the test for halide ions

Answer 1

1. add nitric acid (to remove carbonates)
2. add silver nitrate solution
3. coloured precipitate forms if halide is present

Question 2

Give the precipitate formed for chloride ions (and result with ammonia)

Answer 2

white precipitate
-dissolves in a dilute ammonia solution

Question 3

Give the precipitate formed for bromide ions (and result with ammonia)

Answer 3

cream precipitate
- dissolves in a concentrated ammonia solution

Question 4

Give the precipitate formed for iodide ions (and result with ammonia)

Answer 4

yellow precipitate
- does not dissolve

Question 5

Describe the test for carbonate ions

Answer 5

1. add any dilute acid
2. bubble through limewater
3. if it turns cloudy (from carbon dioxide gas) a carbonate is present

Question 6

Describe the test for sulfate ions

Answer 6

1. add hydrochloric acid (reacts with any carbonate impurities)
2. add aqueousbarium chloride/nitrate solution
3. white precipitate forms if sulfate ions are present

Question 7

Describe the test for ammonium ions

Answer 7

1. add sodium hydroxide
2. warm
3. test gas with damp red litmus - should turn blue if gaseous ammonia has been produced

ammonia also has a strong smell