AQA A-Level Chemistry AS Paper 1, June 2023: Question 22

1 mark · Medium difficulty · Multiple Choice

Identify which substance is present in the filtrate after filtering the reaction mixture formed in Test 2.

Practise this question

Question

Question 22 asks: 'In Test 2, the mixture formed by solution S is filtered. Which substance is present in the filtrate?' followed by four multiple-choice options with tick boxes: A AgBr, B Agl, C Ba(NO3)2, and D Mg(NO3)2. It is worth 1 mark.
Question text

Use this information for Questions 19 to 23.

A student completes some test-tube reactions on five solutions, P, Q, R, S and T.

The student completes each test on separate samples of each solution.

Observations are shown in the table.

Test 1 Test 2 Test 3 Test 4

Solution Add a few drops of Add HNO3(aq) then Add a few drops of Add a few drops of

H2SO4(aq) a few drops of NaOH(aq) Cl2(aq)

21 What observation is expected in Test 2 for solution S?

AgNO3(aq)

[1 mark]

P White precipitate Cream precipitate No visible change Orange solution

A No visible change Effervescence and

Q Effervescence No visible change No visible change

white precipitate

B Effervescence

R No visible change No visible change White precipitate No visible change

C White precipitate

S White precipitate No visible change Dark brown solution

D Pale yellow precipitate

T No visible change White precipitate White precipitate No visible change

22 Use the information in the table to answer QuestionsInTest 2, the mixture formed by solutionSis filtered.19 to 23.

19 Which substance is present in the filtrate?Which solution contains carbonate ions?

[1 mark][1 mark]

AA AgBrSolution P

BB AgSolutionl Q

CC Ba(NOSolution3)2R

DD Mg(NOSolution3)S2

Mark scheme

Show the mark scheme Mark scheme table row for question 22 stating: 'This question was discounted due to a typographical error in option B. All candidates were awarded 1 mark for this item.'

22 This question was discounted due to a typographical error in option B. All candidates were awarded 1 mark for this item.

How to answer it

Precipitation Reactions & Identifying Species in Filtrate

📌 What this question tests

This question assesses practical inorganic chemistry, specifically understanding filtration terminology (distinguishing between residue and filtrate), solubility rules of Group 2 salts and silver halides, and deducing spectator ions remaining dissolved in aqueous solution following a precipitation test.

Question 22 (1 Mark)

Identifying the Dissolved Species in the Filtrate

Multiple Choice Analysis & Official Mark Scheme Verdict

✅ Official Outcome & Scientific Key

Official Mark Scheme Status: Question discounted; all candidates awarded 1 mark.

Underlying Chemical Deduction:

  • Filtrate is the liquid that passes through the filter paper containing soluble dissolved ions.
  • Residue is the insoluble solid retained on the filter paper.
  • Both AgBr and AgI are insoluble precipitates, so they form the residue.
  • Nitrate salts (such as Mg(NO₃)₂ or Ba(NO₃)₂) are highly soluble in water and remain dissolved in the aqueous filtrate.

🧠 Exam Technique: Filtrate vs Residue

  • Always define the physical state: When you read "mixture is filtered", immediately write:
    Residue = Solid (s)
    Filtrate = Aqueous solution (aq)
  • Rule out insoluble options immediately: Because AgBr(s) and AgI(s) are classic precipitates formed during tests for halide ions, neither can be in the filtrate.
  • This instantly eliminates options A and B in questions of this format.

💡 Key Knowledge: Solubilities & Ion Tests

  • Silver Halides (Precipitates):
    • AgCl: White precipitate
    • AgBr: Cream precipitate
    • AgI: Yellow precipitate
  • Group 2 Sulfate & Hydroxide Trends:
    • Sulfate solubility decreases down Group 2: BaSO₄ is insoluble; MgSO₄ is soluble.
    • Hydroxide solubility increases down Group 2: Mg(OH)₂ is sparingly soluble; Ba(OH)₂ is soluble.
  • Nitrates: All common nitrate salts (NO₃⁻) are soluble in water.

❌ Common Errors & Examiner Insight

  • The Typo Discount: Option B was printed with a lowercase letter "l" instead of capital "I" ( Agl instead of AgI ). AQA discounted the item so no student was penalised by typographic ambiguity.
  • Confusing Filtrate with Residue: The most frequent student blunder is picking the precipitate that caused the visual positive test, forgetting that filtration separates the solid precipitate out of the filtrate.
  • Chemical Formula Awareness: Ensure elemental symbols are written precisely: Iodine is always capital I.
Mark Scheme Reference: Question 22 — "This question was discounted due to a typographical error in option B. All candidates were awarded 1 mark for this item."

Topics

Inorganic Chemistry · Required Practicals · 3.2.2 Group 2, The Alkaline Earth Metals · 3.2.3 Group 7(17), The Halogens · Required Practical 4: Carry out simple test-tube reactions to identify Cations and Anions

Question and mark scheme from the AQA A-Level Chemistry examination, AS Paper 1, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.