2 Iodate ions contain iodine and oxygen. They have the formula IOx⁻ where x is an integer.
In this experiment you will determine the value of x in an iodate. You will first react IOx⁻ with an excess of iodide ions, I⁻, to form iodine, I2.
The amount of iodine produced is then determined by titration with thiosulfate ions, S2O3²⁻.
I2(aq) + 2S2O3²⁻(aq) → 2I⁻(aq) + S4O6²⁻(aq)
FB 2 is 0.100 mol dm⁻³ sodium thiosulfate, Na2S2O3.
FB 3 is a solution containing 0.0140 mol dm⁻³ IOx⁻ ions.
FB 4 is dilute sulfuric acid, H2SO4.
FB 5 is 0.500 mol dm⁻³ potassium iodide, KI.
FB 6 is starch indicator.

Q: What topic does this question test?

This question tests Analytical techniques in A-Level Chemistry (syllabus code 9701). It is worth 15 marks.

Q: Which exam paper is this question from?

This question appeared in the Cambridge A-Level Chemistry May/June 2024 examination, Paper 3 Variant 2 (9701_s24_qp_32.pdf).

Question

2 Iodate ions contain iodine and oxygen. They have the formula IOx⁻ where x is an integer.
In this experiment you will determine the value of x in an iodate. You will first react IOx⁻ with an excess of iodide ions, I⁻, to form iodine, I2.
The amount of iodine produced is then determined by titration with thiosulfate ions, S2O3²⁻.
I2(aq) + 2S2O3²⁻(aq) → 2I⁻(aq) + S4O6²⁻(aq)
FB 2 is 0.100 mol dm⁻³ sodium thiosulfate, Na2S2O3.
FB 3 is a solution containing 0.0140 mol dm⁻³ IOx⁻ ions.
FB 4 is dilute sulfuric acid, H2SO4.
FB 5 is 0.500 mol dm⁻³ potassium iodide, KI.
FB 6 is starch indicator.

Oracle Prep · Accepted Answer

Sign up to Oracle Prep to view the full model answer with examiner insights.

📋 Examiner Report & Trap Analysis

🎯 Mark Scheme Breakdown

Unlock the Examiner's Analysis

About This A-Level Chemistry Question

Topic

Source

Practice on Oracle Prep

Related Chemistry Questions