A student performs flame tests and chemical tests on three separate solutions, labelled X, Y and Z. Solution X gives a brick-red flame colour. Solution Y gives a crimson-red flame colour. When dilute hydrochloric acid is added to solution Z, followed by barium chloride solution, a white precipitate forms. Identify the metal cation in solution X, the metal cation in solution Y, and the anion in solution Z, and state the name of the white precipitate formed in solution Z.

Pearson Edexcel International GCSE Chemistry (4CH1) — 2.5 Tests for ions and gases · State · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Solution X: Ca²⁺
Solution Y: Li⁺
Solution Z: SO₄²⁻
White precipitate: BaSO₄

Examiner tips

  • Use the exact flame colour names (brick‑red for Ca²⁺, crimson‑red for Li⁺).
  • State the anion in Z before the precipitate.
  • Give the full name of the precipitate (barium sulfate).

Common mistakes

  • Confusing brick‑red with crimson‑red, leading to wrong cation.
  • Writing ‘sulphate’ instead of ‘sulfate’ (UK spelling).
  • Omitting the name of the precipitate or writing it incorrectly.

Mark scheme (4 marks)

  1. Metal cation in solution X is calcium (Ca²⁺)
  2. Metal cation in solution Y is lithium (Li⁺)
  3. The anion in solution Z is sulfate (SO₄²⁻)
  4. The white precipitate formed in solution Z is barium sulfate

Key terms in this question

flame test · precipitate · cation · anion

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