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A student analyses a sample of ethanol, C₂H₅OH, using a mass spectrometer - OCR Gateway - GCSE Chemistry - Question 21 - 2021 - Paper 2
Question 21
A student analyses a sample of ethanol, C₂H₅OH, using a mass spectrometer. The structure of ethanol is shown. Fig. 21.1 shows the mass spectrum of the ethanol. Th... show full transcript
Worked Solution & Example Answer:A student analyses a sample of ethanol, C₂H₅OH, using a mass spectrometer - OCR Gateway - GCSE Chemistry - Question 21 - 2021 - Paper 2
Step 1
Mass spectrum
Answer
The highest molecular ion peak in the mass spectrum is at 46, which indicates the molecular formula of ethanol (C₂H₅OH). The peak at m/z = 15 is associated with the CH₃ group. Additionally, there are notable peaks at 29 and 31, which typically indicate ethyl and hydroxyl fragments.
Step 2
Infrared spectrum
Answer
The infrared spectrum shows significant peaks in the range of:
- 3230-3550 cm⁻¹, which indicates O-H stretching vibrations.
- 1500-1000 cm⁻¹ that is commonly associated with C-H bending of the alkane group (C-C).
- 1100 cm⁻¹, indicative of C-O stretches from the hydroxyl (C-OH) bond.