Edexcel Jun 2014 (R) Paper 1 Q19 (with explained solutions) |

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Edexcel Jun 2014 (R) Paper 1 Q19

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SECTION B Answer ALL the questions. Write your answers in the spaces provided. 19 Naturally occurring samples of potassium contain three isotopes, 39K, 40K and 41K. (a) The isotopes can be separated in a mass spectrometer. (i) In the diagram below, particles are ionized at A and detected at D. to a pump Name the processes occurring in the mass spectrometer at B and C. (2) BC10 *P42990A01028*<br />
(ii) A sample of potassium has the following composition. Isotope 39K % abundance 93.22 40K 0.12 41K 6.66 Calculate the relative atomic mass of this sample of potassium, giving your answer to two decimal places. (iii) Complete the table below to show the numbers of sub-atomic particles in an atom of each of the isotopes 39K and 41K. Isotope Electrons Protons Neutrons 39K 41K (iv) Complete the electronic configuration for an atom of 39K. (2) (1) (1) 1s2*P42990A01128* 11 Turn over<br />
(v) Why is potassium placed after argon in the Periodic Table, even though it has a smaller relative atomic mass? (1)*(vi) Explain why a potassium ion is smaller than a potassium atom. (2)(b) The type of bonding in potassium is metallic. Draw a labelled diagram to illustrate the metallic bonding in potassium. (2) 12 *P42990A01228*<br />
(c) The graph shows the variation of first ionization energy with atomic number for six successive elements in the Periodic Table, including potassium. The letters used to label the elements are not their symbols. 1st ionization energy / kJ mol1 C D Element (i) Define the term first ionization energy. (3)(ii) Identify, with a reason, which element is potassium. (2)(Total for Question 19 = 16 marks) *P42990A01328* 13 Turn over<br />
BLANK PAGE 14 *P42990A01428*<br />

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$Section B Question Number 19(a)(i) B acceleration (1) Acceptable Answers C deflection (1) Allow B ions are accelerated/ accelerating C ions are (being) deflected Question Number 19(a)(ii) Acceptable Answers Reject B just electric field C just magnetic field Mark (Ar for K) = (39 x 0.9322) + (40 x 0.0012) + (41 x 0.0666) or a correct fraction using percentages (1) = 39.1344 = 39.13 (1) Correct answer without working scores 2 Max 1 if not to 2 decimal places Second mark dependent on first IGNORE Units of any kind (e.g. g, g mol1, amu, etc.) Question Number 19(a)(iii) Acceptable Answers Isotope Electrons Protons Neutrons 39K 41K 19 19 19 19 20 22 Reject Mark Reject Mark 6CH0101R 1406<br /> Question Number 19(a) (iv) Acceptable Answers Question Number 19(a)(v) (Position in the Periodic Table) depends upon atomic number / proton number OR Ar (atom) has (one) fewer proton(s) (than K atom) OR K (atom) has (one) more proton(s) (than Ar atom) OR K has atomic number 19 (whereas) Ar has atomic number 18 OR Ar has 18 protons, K has 19 protons IGNORE Elements are not arranged in order of (relative) atomic mass IGNORE Mention of numbers of electrons / numbers of shells (of electrons) IGNORE Arranged in vertical groups in accordance to properties / argon is a noble gas Acceptable Answers (1s2) 2s22p6 3s23p6 4s1 Fully correct Ignore additional 1s2 Reject Reject Mark Mark 6CH0101R 1406<br /> Question Number 19(a) (vi) Question Number 19(b) Acceptable Answers One fewer shell of electrons (1) Electrons in the ion are held more tightly OR Same number of protons attracting fewer electrons OR Less repulsion between (remaining) electrons (1) IGNORE References to effective nuclear charge / charge density Reject Mark Reject Mark Acceptable Answers Regular lattice of singly-positively charged (potassium) ions Delocalised electrons / sea of electrons / mobile electrons (1) (1) e.g. Accept other regular arrangements Unlabelled diagram max (1) 6CH0101R 1406<br /> Acceptable Answers Reject Question Number 19(c)(i) Mark Energy given out for first mark Just gaseous element/ gaseous substance (1) (1) (1) First mark:- Makes mention of energy/enthalpy/(heat) energy/heat (change) AND to remove an electron Second mark: one mole/1 mol Third mark: Makes mention of gaseous atom(s) ALTERNATIVE ANSWER Energy change per mole for (1) X(g)X+(g) + e() (2) One mark for species One mark for correct state symbols Mark independently IGNORE any references to standard conditions Acceptable Answers Question Number 19(c)(ii) Potassium is E (1) Reject Mark Alkali metals always have the lowest first ionization energy in their period OR It follows a noble gas/ an element with very high first ionization energy OR Ionization energy falls (significantly) at the start of a (new) period / Ionization energy falls (significantly) after D (1) Total for Q19 = 16 marks 6CH0101R 1406<br />$

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