Pearson Edexcel International GCSE in Chemistry · 4CH1 · Free · no account needed
Tests for Ions — exam questions
12 original Incandio exam-style questions on Tests for Ions, 26 marks, about 26 minutes of writing. Each one carries the command word, the tariff and the specification statement it assesses, exactly as a paper presents them. This is an original Incandio practice question, written to reflect the structure and demands of the qualification. It is not an official Pearson Edexcel past-paper question.
This is the practice set for Tests for Ions — the lesson that teaches it. Read the lesson first if the idea is new; come here when you want to find out whether you can turn it into marks. Completely free, no account needed to read.
What these questions ask of you
7 command words run through this set, and on Pearson Edexcel International GCSE Chemistry each one means something precise. Answering the wrong command is the commonest way a candidate who understands the lesson still loses the mark.
- Which (1 mark)
- one option chosen from the set given
- Give (1–2 marks)
- a short factual answer — the most common chemistry command
- Name (1 mark)
- the correct chemical name
- Describe (2–5 marks)
- developed, linked statements of what happens or what is observed Misread as: giving one bare observation where the tariff asked for a developed account
- Explain (2–4 marks)
- the reason, in terms of particles, bonding, energy or equilibrium Misread as: describing the observation without giving the chemistry that causes it
- Suggest (1–3 marks)
- a plausible answer applying taught chemistry to an unfamiliar substance
- Identify (1–2 marks)
- the correct substance or feature selected from what is given
Assessed on Paper 1 (4CH1/1C) and Paper 2 (4CH1/2C), against AO1, AO2, AO3.
Where these sit in the specification
Pearson Edexcel International GCSE Chemistry (4CH1) — statements 2.47 · 2.48. Incandio is aligned to this specification; it is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording.
The 12 questions
Answer them on paper, then open the lesson's exam practice to have them marked. The mark scheme, the accepted and rejected answers and the annotated model answer are in Incandio and are not printed here — an answer beside its question is not practice.
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Table 1 — adding sodium hydroxide solution to four solutions Solution With a little sodium hydroxide On warming A blue precipitate no further change B green precipitate no further change C brown precipitate no further change D no precipitate pungent gas turns damp red litmus blue Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(a)
(1)Identify
Identify the ion present in solution C of Table 1.
Table 1 — adding sodium hydroxide solution to four solutions Solution With a little sodium hydroxide On warming A blue precipitate no further change B green precipitate no further change C brown precipitate no further change D no precipitate pungent gas turns damp red litmus blue Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(b)
(2)Give
Give the ions present in solutions A and B of Table 1.
Table 1 — adding sodium hydroxide solution to four solutions Solution With a little sodium hydroxide On warming A blue precipitate no further change B green precipitate no further change C brown precipitate no further change D no precipitate pungent gas turns damp red litmus blue Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(c)
(3)Explain
Explain how solution D in Table 1 behaves differently from the other three, and what this shows.
Table 1 — adding sodium hydroxide solution to four solutions Solution With a little sodium hydroxide On warming A blue precipitate no further change B green precipitate no further change C brown precipitate no further change D no precipitate pungent gas turns damp red litmus blue Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(d)
(3)Suggest
A student tested solution A for a halide but forgot the nitric acid, and reported a positive result. Suggest why her conclusion cannot be trusted.
Table 1 — adding sodium hydroxide solution to four solutions Solution With a little sodium hydroxide On warming A blue precipitate no further change B green precipitate no further change C brown precipitate no further change D no precipitate pungent gas turns damp red litmus blue Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(Total for Question 1 = 9 marks)
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(1)Which
Which ion gives a blue precipitate with sodium hydroxide solution?
Ion A iron(II) B iron(III) C copper(II) D ammonium (Total for Question 2 = 1 mark)
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(1)Give
Give the colour of the precipitate formed when silver nitrate is added to an acidified chloride solution.
Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(Total for Question 3 = 1 mark)
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(1)Name
Name the reagent added after dilute hydrochloric acid when testing for a sulfate ion.
Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(Total for Question 4 = 1 mark)
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(2)Describe
Describe the test for an ammonium ion and the result that confirms it.
(Total for Question 5 = 2 marks)
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(3)Explain
Explain why dilute nitric acid is added before the silver nitrate in the test for a halide ion.
Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(Total for Question 6 = 3 marks)
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(2)Explain
Explain why sodium hydroxide solution produces a precipitate with copper(II) ions but not with sodium ions.
(Total for Question 7 = 2 marks)
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(3)Suggest
Suggest a sequence of tests that would identify a solution as iron(III) sulfate, and say what each test would show.
Tests for negative ions — Halides: add dilute nitric acid, then silver nitrate solution — chloride gives white, bromide cream, iodide yellow. Sulfate: add dilute hydrochloric acid, then barium chloride solution — a white precipitate forms. Carbonate: add dilute acid — fizzing, and the gas turns limewater milky.
(Total for Question 8 = 3 marks)
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(4)Explain
Explain why dilute nitric acid is added before barium chloride when testing for sulfate ions, and why hydrochloric acid must not be used instead.
(Total for Question 9 = 4 marks)
Have them marked, then defend the answer
Practice tells you the mark; teaching it back tells you whether you understand it. On Incandio a topic counts as mastered only once you have taught it and defended it.
- Mark these questions — 12 questions, marked on Incandio against the authored scheme, with the mistake you actually made named.
- Teach it — explain Tests for Ions to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against Carl Remigius Fresenius over three rounds, marked against descriptors you can read first.
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Back to the lesson
- Tests for Ions — Sodium hydroxide identifies four cations by the colour of what falls out — and three anion tests complete the set.
- All of Incandio Chemistry · Incandio Exam Practice