Edexcel Jun 2010 Paper 1 Q16 (with explained solutions) |

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Edexcel Jun 2010 Paper 1 Q16

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PMT 16 The diagram below shows a mass spectrometer, which can be used to determine the percentage abundances of isotopes in an element. sample vaporized electron beam ionizes atoms electric field magnetic field recorder amplifier ions are detected and recorded (a) Explain, in terms of sub-atomic particles, what is meant by the term isotopes. (2)(b) Describe the role of the following parts of the mass spectrometer. (i) Electric field (1)(ii) Magnetic field (1)14 *N35691A01428*<br />
PMT (2) (2) (c) A sample of the element barium is made up of four isotopes. The data below were taken from a mass spectrum of this sample. Mass/charge ratio % abundance 135 136 137 138 9.01 10.81 12.32 67.86 Calculate the relative atomic mass of the sample, giving your answer to one decimal place. (d) The element bromine has two stable isotopes, 79Br and 81Br. How many peaks + ions would be seen in the mass spectrum of bromine? corresponding to Br2 Justify your answer.(e) Suggest another application of mass spectrometry, other than to determine the relative atomic mass of an element. (1)(Total for Question 16 = 9 marks) *N35691A01528* 15 Turn over<br />

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Question Number 16 (a) Question Number 16 (b)(i) Question Number 16 (b) (ii) Question Number 16 (c) Acceptable Answers Reject Mark Atoms (of an element) with the same number of protons (1) But with different number of neutrons (1) Same atomic number but different mass number only = (1) Element(s) with same number of protons but different number of neutrons = (1) max Ignore comments on electrons unless incorrect in which case award max 1 Acceptable Answers Reject Mark (Electric field) accelerates ions Acceptable Answers (Magnetic field) deflects / changes direction of / bends the beam of ions if the term ions is missing or an incorrect term is used e.g. atoms, penalise only once in parts b (i) and b (ii) Reject Mark just bends ions Acceptable Answers Reject Mark % abundance = (135 x 9.01 + 136 x 10.81 + 137 x 12.32 + 138 x 67.86) /100 (1) = 137.4 (1) ignore units Allow TE for one slip in transfer of data from question Correct answer scores (2) Just 137 as final answer 137.39 137.3903 137.390 6CH0101 1006<br />
Acceptable Answers Reject Mark + ions) (1) three peaks (caused by Br2 because ions (79Br-79Br)(+) and (81Br-79Br)(+) / (79Br-81Br)(+) and (81Br-81Br)(+) (1) Mark independently Acceptable Answers Reject Mark Any one analysis of material from space / drug testing in sport / identify breakdown products from drugs in body / quality control in pharmaceutical industry / identify molecules from sample with potential biological activity / radioactive dating with context e.g determine age of fossils / human remains The uses above must have a context / determining Mr of a molecule / evidence for structure from fragmentation pattern Question Number 16 (d) Question Number 16 (e) 6CH0101 1006<br />

Question 15 16 17 18

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