8.7 Required practical: identifying ions
5 exam questions worth 8 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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A solid gives a yellow flame and a cream precipitate with nitric acid and silver nitrate. What is it?
Choose one answer.
Correct Not quite: the answer is Sodium bromide
Mark scheme
A
Model answer
A: yellow flame = sodium; cream precipitate = bromide.
A green solid gives a green precipitate with sodium hydroxide solution, and a white precipitate with hydrochloric acid and barium chloride.
Identify the compound.
Mark scheme
- iron(II) (1)
- sulfate: iron(II) sulfate (1)
Model answer
Iron(II) sulfate, FeSO4.
Explain why a fresh sample of the solution is used for each test.
Mark scheme
- so reagents from one test do not interfere with / give false results in the next (1)
Model answer
The chemicals added in one test could react in the next test and give a false result.
A white solid gives an orange-red flame, and fizzes with dilute acid, producing a gas that turns limewater milky.
Name the solid.
Mark scheme
- calcium (1)
- carbonate: calcium carbonate (1)
Model answer
Calcium carbonate.
Give one hazard in this practical and a precaution to reduce the risk.
Mark scheme
- e.g. barium chloride is toxic / sodium hydroxide is corrosive / silver nitrate stains skin (1)
- wear gloves / eye protection, use small amounts (1)
Model answer
Sodium hydroxide is corrosive, so wear eye protection.
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