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6 (a) Substance X is an ammonium salt - Edexcel - GCSE Chemistry - Question 6 - 2013 - Paper 1
Question 6
6 (a) Substance X is an ammonium salt. (i) Complete the sentence by putting a cross (✗) in the box next to your answer. A test was carried out to find which anion ... show full transcript
Worked Solution & Example Answer:6 (a) Substance X is an ammonium salt - Edexcel - GCSE Chemistry - Question 6 - 2013 - Paper 1
Step 1
Complete the sentence by putting a cross (✗) in the box next to your answer.
Answer
The anion present in substance X is A carbonate ion, CO₃²⁻. This conclusion is based on the effervescence observed when the acid was added, which indicates that a carbonate is present as it reacts with the acid to release carbon dioxide gas, turning limewater milky.
Step 2
Describe how sodium hydroxide solution can be used to show that ammonium ions are present in substance X.
Answer
To test for ammonium ions, add a few drops of sodium hydroxide solution to substance X and gently heat the mixture. If ammonium ions are present, ammonia gas will be released, which can be detected by its characteristic smell or by using damp red litmus paper that will turn blue in the presence of ammonia.
Step 3
Step 4
Explain how, using chemical tests, the technician could find out if the substance left in the beaker was potassium sulfate, potassium iodide, sodium sulfate or sodium iodide.
Answer
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Test for cation using flame test:
- Make a solution of the crystals in water.
- Dip a clean wire loop into the solution and place it in a flame.
- If the flame is yellow, sodium ions are present, if it is lilac, potassium ions are present.
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Test for iodide ions:
- Make a solution of the crystals in water.
- Add dilute nitric acid followed by silver nitrate solution.
- If a yellow precipitate forms, iodide ions are present:
ightarrow AgI $$
- If no precipitate forms, sulfuric ions may be present.
- Test for sulfate ions:
- Add hydrochloric acid followed by barium chloride solution.
- If a white precipitate forms, sulfate ions are present:
ightarrow BaSO_4 $$