This is a question about time of flight (TOF) mass spectrometry.
Give the equation, including state symbols, for the formation of Mg+\text{Mg}^+Mg+ ions from Mg\text{Mg}Mg atoms by electron impact.
A sample of magnesium is analysed by TOF mass spectrometry. The sample is ionised using electron impact. The ions are accelerated to have a kinetic energy (KEKEKE) of 1.91×10−18 J1.91 \times 10^{-18}\text{ J}1.91×10−18 J. An ion takes 1.25×10−4 s1.25 \times 10^{-4}\text{ s}1.25×10−4 s to travel along a 120.0 cm120.0\text{ cm}120.0 cm flight tube.
KE=12mv2 KE = \frac{1}{2}mv^2 KE=21mv2where m=mass (kg)m = \text{mass (kg)}m=mass (kg) and v=speed (m s−1)v = \text{speed (m s}^{-1}\text{)}v=speed (m s−1). Use the information given to deduce the mass number of this ion. The Avogadro constant, L=6.022×1023 mol−1L = 6.022 \times 10^{23}\text{ mol}^{-1}L=6.022×1023 mol−1.
Explain how the ions are detected in the TOF mass spectrometer. State how the relative abundance of the ions is determined.
A sample of magnesium contains three isotopes, 24Mg^{24}\text{Mg}24Mg, 25Mg^{25}\text{Mg}25Mg and 26Mg^{26}\text{Mg}26Mg. 79%79\%79% of the sample is 24Mg^{24}\text{Mg}24Mg. The other isotopes are in a 1:21:21:2 ratio of 25Mg:26Mg^{25}\text{Mg} : ^{26}\text{Mg}25Mg:26Mg. Calculate the percentage abundance of 26Mg^{26}\text{Mg}26Mg in this sample. Use your answer to deduce the relative atomic mass (ArA_rAr) of the sample. Give your answer to 1 decimal place.
Electrospray ionisation is used instead of electron impact for the ionisation of a protein in a mass spectrometry experiment. Suggest why.
33 exam-style questions on AQA A Level Chemistry Atomic structure, covering Fundamental particles, Mass number and isotopes, and Electron configuration. Each one has a worked solution and a mark scheme showing where the marks go.