A-LevelChemistryAnalytical techniquesOct/Nov 2025Paper 1 Q401 Mark
The purity of a compound can be determined using infrared spectroscopy. The table gives the characteristic infrared absorption frequencies for some selected bonds. [Figure 40: Table of IR absorption frequencies] Propan-2-ol is made by hydration of propene. A sample of the product is obtained. Which feature of the infrared spectrum of the product would show that no propene remains in the product?
Aabsorption in the 2900 cm⁻¹ region
Bstrong absorption below 1000 cm⁻¹
Cthe lack of absorption at or near 1250 cm⁻¹
Dthe lack of absorption at or near 1550 cm⁻¹
✓ Correct Answer
The correct answer is D: the lack of absorption at or near 1550 cm⁻¹
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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