AQA A-Level Chemistry AS Paper 1, November 2021: Question 20

1 mark · Medium difficulty · Multiple Choice

Identify which solid sodium halide does not produce a sulfur-containing gas when reacted with concentrated sulfuric acid.

Practise this question

Question

Multiple choice question asking which solid sodium halide does not produce a sulfur-containing gas as one of the products when reacted with concentrated sulfuric acid. The options are A: NaCl, B: NaBr, C: NaI, and D: NaAt, each with a corresponding answer box.
Question text

20 Some solid sodium halides are reacted with concentrated sulfuric acid.

Which solid sodium halide does not produce a sulfur-containing gas as one of the

products?

[1 mark]

A NaCl

B NaBr

C NaI

D NaAt

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer is A, corresponding to NaCl, for 1 mark.

20 A 1 NaCl

How to answer it

Reactions of Solid Sodium Halides with Concentrated Sulfuric Acid

What this question tests

This question assesses your knowledge of the trends in reducing ability of halide ions (Cl⁻, Br⁻, I⁻, At⁻) down Group 7, and their subsequent redox reactions with concentrated sulfuric acid (H₂SO₄).

Question 20 [1 Mark]

Multiple Choice Answer & Breakdown

✅ Correct Answer

A (NaCl)

Awarded 1 mark for selecting option A.

💡 Key Knowledge

  • Chloride ions (Cl⁻) are not strong enough reducing agents to reduce the sulfur in concentrated H₂SO₄.
  • Only an acid-base reaction occurs, producing steamy fumes of hydrogen chloride ( HCl ) gas and sodium hydrogensulfate ( NaHSO₄ ). No sulfur-containing reduction products (like SO₂, S, or H₂S) are formed.

🧠 Exam Technique

Recall the trend down Group 7: reducing ability increases down the group.
• NaCl undergoes only acid-base reaction.
• NaBr reduces H₂SO₄ to sulfur dioxide ( SO₂ ).
• NaI reduces H₂SO₄ further to sulfur ( S ) and hydrogen sulfide ( H₂S ).

❌ Common Errors

Students sometimes confuse the observation of misty/steamy fumes with sulfur-containing gases. Remember, HCl contains chlorine and hydrogen, not sulfur!

Topics

Inorganic Chemistry · 3.2.3 Group 7(17), The Halogens

Question and mark scheme from the AQA A-Level Chemistry examination, AS Paper 1, November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.