--# OCR RECOGNISING ACHIEVEMENT. CHEMISTRY Foundation Chemistry 1O JUNE 2OO4. t hour TIME. INSTRUCTIONS TO CANDIDATES o o e r o

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1 --# OCR RECOGNISING ACHIEVEMENT OXFORD CAMBRIDGE AND RSA EXAMINATIONS Advanced Subsidiary GCE CHEMISTRY Foundation Chemistry Thursday 1O JUNE 2OO4 Morning 2811 t hour Candidates answer on the question paper. Additional materials: Data Sheet for Chemistry Scientific Calculator Candidate Name Centre Number Candidate Number TIME t hour INSTRUCTIONS TO CANDIDATES o o e r o Write your name in the space above. Write your Centre number and Candidate number in lhe boxes above. Answer all the questions. Write your answers in the spaces provided on the question paper. Bead each question carelully and make sure you know what you have to do before starting your answer. INFORMATION FOR CANDIDATES. The number of marks is given in brackets I lat the end of each question or part question. o You will be awarded marks for the quality of written communication where this is indicated in the question. FOR EXAMINER'S USE. You may use a scientific calculator. Qu. Max. Mark. You may use the Data Sheet for Chemistry You are advised to show all the steps in any calculations TOTAL 60 sp (sm/slm) /4 o ocr 2oo4 [Mfiool3423l This question paper consists of 12 printed pages. Registered Charity Number: [Turn over

2 2 Answer all the questions. Examinels 1 A fifty pence coin contains nickel alloyed with a metal A. (a) Nickel exists as a mixture of three isotopes, nickel-s8, nickel-60 and nickel-62. Complete the table below to show the atomic structures of the isotopes in metallic nickel. isotope protons neutrons electrons nickel-58 nickel-60 nickel-62 t3l (b) Metal A can be identified from its relative atomic mass. Analysis of a fifty pence coin showed that two isotopes of metal A were present with the following percentage abundances. isotope isotope 1 isotope 2 relative isotopic mass % abundance (i) What analytical method is used to obtain this information? (ii) Define the term relative atomic mass....t11

3 (iii) Calculate the relative atomic mass of the sample of metal A. Give your answer to three significant figures. 3 Examine/s answer t2l (iv) your answer to (b)(iii) and the Data Sheeto suggest the identify of metal A. (c) Nickel makes up 25"h of the total mass of a fifty pence coin. A fifty pence coin has a mass of 8.0 g. (i) Calculate how many moles of nickel atoms are in a fifty pence coin...t11 answer.. mol t2l (ii) Calculate the number of atoms of nickel in a fifty pence coin. L =6.02 x 1023mol-1 answer.. atoms t1 l [Total: 13] [Turn over

4 4 2 Magnesium, fluorine and magnesium fluoride have differentypes of bonding and different properties. Examiner's (a) Magnesium has metallic bonding. (i) Draw a diagram to show what is meant by metal/ic bonding. Label the diagram. (ii) Why is magnesium a good conductor of electricity?..t11 (b) Fluorine, F, has covalent bonding. (i) State what is meant by a covalent bond....t21 (ii) Draw a'dot-and-cross'diagram to show the covalent bonding in fluorine. Show outer electron shells only. t1l

5 (c) Magnesium fluoride, MgF, has ionic bonding. 5 Examine/s (i) How does ionic bonding hold particles in MgF, together?,.,,t2] (ii) Draw a'dot-and-cross'diagram for magnesium fluoride, MgFz.Show outer electron shells only. (iii) Magnesium fluoride is produced when magnesium reacts with fluorine. Complete the half-equations below to show the formation of the ions in magnesium fluoride in this reaction. Mg+ + F2 + -) (iv) A student found that magnesium fluoride has different electrical conductivities when solid and when dissolved in water. Explain these two observations. t2l...t21 [Total : 14] [Turn over

6 3 A household bleach contains sodium chlorate(l), NaClO, as its active ingredient. 6 The concentration of NaCIO in the bleach can be found by using its reaction with hydrogen peroxide,hror. NaCIO(aq) +HrOr(aQ) +O2(g) +NaOl(aq) +H2O(l) (a) Chlorine has been reduced in this reaction. oxidation numbers to prove this. Examinels..121 (b) A student added an excess of aqueous hydrogen peroxide to 5.0cm3 of the bleach. 84 cm3 of oxygen gas were released. (i) How many moles of O, were released? Assume that, under the laboratory conditions, 1.00 mol of gas molecules occupies 24 dm3. answer.. mol t1l (ii) How many moles of NaCIO were in 5.Ocm3 of the bleach? answer.. mol t1l (iii) What was the concentration, in mo! dm-3, of NaCIO in the bleach? answer.. mol dm-3 t1l

7 7 (c) The label on the bottle of household bleach states that the bleach contains a minimum of 4.5 g per 100 cm3 of NaClO. your answer to (b)(iii) to decide whether or not the information on the label is correct. Examinels (d) lt is extremely importanthat household bleach is not used with acids. This is because a reaction takes place that releases toxic chlorine gas. Suggest an equation for the reaction of an excess of hydrochloric acid with household bleach. t3l..t21 [Total: 10] [Turn over

8 4 This question is about elements and compounds of Group 2 of the Periodic Table. I Examinef s (a) When calcium is added to water, a vigorous reaction takes place, releasing hydrogen gas. Ca(s) + 2H2O(l) -+ Ca(OH)r(aq) + H2(g) (i) Suggest a value for the ph of the solution formed in this reaction. (ii) Complete the electroniconfiguration of calcium in..t11 Ca(s) 1s22s22p Ca(OH)r(aq) 1s22s22p tzl (b) Carbon dioxide is bubbled through aqueous calcium hydroxide. (i) A milky white precipitate A forms. ldentify precipitate A and write down an equation for its formation. identity of precipitate A... eq uation t2l (ii) As more carbon dioxide is bubbled through the solution, precipitate A disappears and a colourlessolution B forms. ldentify solution B and write down an equation for its formation. identity of solution B.. equation (iii) Dilute hydrochloric acid is added to solution B. A gas is given off and a colourless solution C forms. Suggesthe identity of solution C.

9 I (c) When barium metal is added to water, the reaction taking place is much more vigorous than with calcium. Explain why barium is more reactive than calcium. Examinels " " " " 1 ' l.41 [Total: 12] [Turn over

10 5 In this question, one mark is available for the quality of written communication. 10 Examinef s (a) Describe the intermolecular bonding in CHo and in HrO. clear diagrams in your answer. t6l (b) State and explain two anomalous properties of HrO that depend on its intermolecular forces. 14l Quality of Written Communication I1l [Total: 11]

11 Final Mark Scheme 2811 June 2004 Question Expected Answers Marks 1 (a) (b) (i) ( ii) (iii) (iv) isotope nickel-58 nickel-60 nickel-62 protons neutrons r' ecf, 3rd column same as first column. electrons mass spectrometry / mass spec... /mass spectrometer should also be credited average mass/weighted mean mass of an atom / compared with carbon-12 / 1l12th of mass of carbon-1zon a scale where carbon-12 is 12/ mass of I mole of atoms (of an element) mass of I mole of carbon-l2 is equivalento first two marks "mass of the elementhat contains the same number of atoms as are in 1 mole of carbon-l2" ---) 2 marks (mark lost because of mass units) 63.0 x x / / = 63.5 (mark for significant figures) / copper/ Cu { t3l 11l 13I 11I (c) (i) ( ii) mass of Ni = 2.0.g / moles of Ni = mol = mol / (1 mark would typically result from no use oi 25% mol) 2nd mark is for the mass of Ni divided by 58.7 number of atoms of Ni = 6.02 x 1023 x = 2.05 x 1022 t 2.1 x 1022 atoms r' Can be rounded down to 2.1 or 2.0 or 2 (if 2.0) From B g, ans = 8.1 BlB.2 x 1022 (and other consequential responses) I2l t1i Total: 13

12 Final Mark Scheme 2811 June 2004 Question Expected Answers Marks (a) (i) positive ions/cations / and negative electrons / Can be described in words only for both marks I2l ( ii) contain free/mobile/delocalised electrons / 11I (b) (i) shared pair of /electrons r' i.e. 'shared electrons'is worth 1 mark. pair of electrons for second marks (i i) correct dot-and cross diagram / tll (c) (i) electrostatic attraction / between oppositely charged ions / (charged or electrostatic for 1st mark) ( :i) correct dot-and cross diagram / correct charges / (iii) Mg Mgt* + 2e- / F 2 + 2e- ----) 2F- / - s,gn not required with electron azl (iv) solid: ions cannot move /in fixed positions in lattice / solution: ions are free to move r' tzl Total:14

13 Final Mark Scheme 2811 June 2004 Question Expected Answers Marks (a) NaClO, oxidation state = *1 v NaCf, oxidation state = -1 / OR Oxidation number decreases from NaCIO -e NaCl / by2/ (b) (i) = 3. 5 x 10-s mol / t1i ( ii) 3.5 x 10-3 mol / ans to (i) 11I (iii) 3.5 x 10-3 x 1000/5 = 0.70 mol dm-3 / ans fo (ii) x 1A00/5 11I (c) mofar mass of NaCIO = =74.5 (g mol-') r concentration = 0.70 x74.5 = g (dm-3; ans fo (iii) x 74.5 bleach is g per 100 cm3 and the information is correct (as this value exceeds 4.5o/o) / t3l response depends upon answer to (b)(iii). Could be opposite argument if ans < 4.5% OR molar mass of NaCIO = b =74.5 (g mol-') t moles of NaOCI = 4.5t74.5 = mol (in 100 cm3; ; bleach is 10 x = mol dm-3 which is less than answer to (b)(iii) and therefore label is correct. / response depends upon answerto (b)(iii). Could be opposite argument if ans (d) 2HCl + NaCIO ---+ Cl2 + NaCl + HrO t,r Award one mark for: HCI + NaCIO --) Cl2 + NaOH Total: 10

14 Final Mark Scheme 2811 June 2OO4 Question Expected Answers Marks (a) (i) Answer is inclusive of I - 14 inclusive / 11I ( ii) Ca(s): 1s22s22pu3s'3pu4 s' / ca(oh)2(aq): 1 s22s22pu3s' 3pu./ (b) (i) ldentity of precipitate A: calcium carbonate I CaCO, / Equation: Ca(OH)2 + COz --> CaCOs + H2O / equation alone would score 2 marks unless contradicted by identity ( ii) mula of solution B: Ca(HCOs)z,/ Equation: CaCOs + HzO + CO, Ca(HCO iz { equation alone would score 2 marks unless contradicted by identity ( iii) CaCl, / tli (c) barium atoms are larger / barium atoms have more shielding / this outweighs the increase in nuclear charge / barium electrons are lost more easily /less energy required /ionisation energy decreases / l4l Total:12

15 Final Mark Scheme 2811 June 2004 Question Expected Answers Marks (a) HzO H bonding from O of 1 molecule to H of another / dipoles shown or described / with lone pair of O involved in the bond / CHa van der Waals' forces from oscillating dipoles/ temporary dipoles/ transient dipoles/ instantaneous dipoles / l3i (b) leading to induced dipoles / caused by uneven distribution of electrons / Two properties from: lce is less dense/lighter at 4'C / than waterlfloats on water/ max density exptanation:,, ffi:$iil[.;1]":.,'"s apart l3l sub-total:6 Higher melting/boiling point than expected / Nofiusf high Accept:'unusually high/strangely highhelatively high' explanation: H bonds need to be broken / must imply that intermolecular bonds are broken l2i High surface tension / explanation strength of H bonds across surface / QoWC over whole question 11I - legible text with accurate spelling, punctuation and grammar { mark 2 properties only 4 max Total: 11

Subject: Foundation Chemistry Code: Session: June Year: Final Mark Scheme

Subject: Foundation Chemistry Code: : : Mark MAXIMUM MARK 60 Mark Page 2 of 7 ADVICE TO EXAMINERS ON THE ANNOTATION OF SCRIPTS 1. Please ensure that you use the final version of the Mark. You are advised