Mass spectrometry and relative atomic massAQA A-Level Chemistry: Mind map

Exam questions on Mass spectrometry and relative atomic mass

1. A chemist analyses a sample of copper in a time of flight (TOF) mass spectrometer. The sample is vaporised and ionised by electron impact to form ions with a 1+ charge. The ions are accelerated by an electric field, drift along a flight tube and then reach a detector. Copper has two isotopes, ⁶³Cu and ⁶⁵Cu.
   Explain why the ions must be accelerated to the same kinetic energy in a TOF mass spectrometer.2 marks
2. A sample of neon gas from the air is analysed in a mass spectrometer. The sample contains three isotopes, with these relative abundances: ²⁰Ne 90.5%, ²¹Ne 0.3% and ²²Ne 9.2%.
   A second sample of neon is enriched in the lighter isotope. It contains only ²⁰Ne and ²²Ne, with relative abundances of 80.0% and 20.0%. Calculate the relative atomic mass of this sample to 3 significant figures.2 marks
3. A mass spectrometer is used to analyse a sample of an unknown metal. The ions detected are all 1+ ions. The mass-to-charge ratios (m/z) of the peaks and their relative abundances are: m/z 54, 5.8%; m/z 56, 91.8%; m/z 57, 2.1%; m/z 58, 0.3%.
   Calculate the relative atomic mass of the metal to 1 decimal place, and use the periodic table to identify the element.3 marks