Edexcel Jun 2015 Paper 1 Q17

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SECTION B Answer ALL the questions. Write your answers in the spaces provided. 17 This question is about the use of mass spectrometers. (a) Bromine has two isotopes, 79Br and 81Br. Explain the term isotopes, by reference to sub-atomic particles. (1)(b) The presence and abundance of these isotopes can be determined by using a mass spectrometer such as that shown in the diagram below. electric field sample vaporized recorder amplifier ions are detected and recorded (i) Explain how ions are produced in the area labelled A. (2)(ii) State what is used to deflect the ions moving through the mass spectrometer in the area labelled B. (1)(iii) Explain why there is a vacuum in a mass spectrometer. (1)*P44879A01124* 11 Turn over<br /> (c) Complete the mass spectrum below for a sample of bromine gas that contains approximately half 79Br isotope and half 81Br isotope. (4) Relative intensity 70 80 90 100 110 130 140 150 160 120 m/e (d) Calculate the relative atomic mass of bromine for a sample which was found to contain 47.0% 79Br and 53.0% 81Br. Give your answer to three significant figures. (e) What would be the effect, if any, on the m/e value of the peak if the ion detected had lost two electrons rather than one electron? (2) (1)12 *P44879A01224*<br /> *(f) One of the uses of mass spectrometers is for the detection of banned substances, such as anabolic steroids, in a blood or urine sample taken from competitors in sports events. (i) Suggest two precautions that are necessary to ensure that the result of any analysis would be valid. (2)(ii) These substances can give competitors an unfair advantage. Suggest why the use of these substances may be of concern to the user. (1)(g) Suggest one other use for mass spectrometers. (1)(Total for Question 17 = 16 marks) *P44879A01324* 13 Turn over<br />

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