High-resolution mass spectrometry and chromatographyEdexcel International A Level Chemistry: Mind map

Exam questions on High-resolution mass spectrometry and chromatography

1. Carbon monoxide, nitrogen and ethene all have the same nominal relative molecular mass of 28. A chemist uses a high-resolution mass spectrometer to analyse gases. Accurate relative atomic masses: H = 1.0078, C = 12.0000, N = 14.0031, O = 15.9949.
   Calculate the accurate relative molecular mass of propanone, C₃H₆O, to four decimal places.2 marks
2. A student uses one-way paper chromatography to separate a mixture of two coloured food dyes, X and Y, using water as the solvent. The solvent front moves 8.0 cm from the pencil start line. The centre of the spot for dye X is 3.2 cm from the start line and the centre of the spot for dye Y is 5.6 cm from the start line.
   Explain why dye Y travels further up the paper than dye X.2 marks
3. A sports laboratory tests an athlete's urine sample for a banned stimulant using gas chromatography combined with mass spectrometry (GC-MS). A peak with retention time 4.2 minutes matches the retention time of a standard sample of the stimulant, which has the formula C₁₀H₁₅N. The mass spectrometer gives a molecular ion peak at m/z 149.1201 for this peak. Accurate relative atomic masses: H = 1.0078, C = 12.0000, N = 14.0031, O = 15.9949.
   Explain why combining gas chromatography with mass spectrometry gives a more reliable identification of the stimulant than gas chromatography alone.3 marks