A3 - Qualitative Analysis

Question 1

What is the test and results for ammonium ions?

Answer 1

1. Add sodium hydroxide to sample
2. Warm solution
3. Place damp red litmus paper/indicator paper near mouth often test tube
4. If ammonium ions present, indicator paper will turn blue

Question 2

What is the test and results for carbonate ions?

Answer 2

1. Add dilute nitric acid to sample
2. If you see bubbles, the compounds could be a carbonate
3. Test the gas evolved by bubbling it through limewater
4. If there are carbonate ions present in the test-tube, then the limewater will turn cloudy

Question 3

What is the test and results for sulphate ions?

Answer 3

1. Add dilute nitric acid to the sample to remove carbonate ions
2. Add barium chloride
3. If there are sulphate ions present in the test-tube, then you will see a white precipitate

Question 4

What is the test and results for halide ions?

Answer 4

1. Add dilute nitric acid to the sample to remove carbonate ions
2. Add silver nitrate
3. If halide ions are present in the sample then you will see a precipitate:
   - White precipitate: chloride ions
   - Cream precipitate: bromide ion
   - Yellow precipitate: Iodide ion

Question 5

What is the order of tests for cations? What acrostic can I use to help remember this?

Answer 5

1. Carbonate
2. Sulphate
3. Halide

CaSH