OCR A Specimen Paper 1 Q19 (with explained solutions) |

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OCR A Specimen Paper 1 Q19

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18 19 This question is about the chemistry of the elements in Group 2 and the halogens. (a) A student prepares an aqueous solution of magnesium chloride by reacting magnesium with excess hydrochloric acid. Write an equation, including state symbols, for this reaction and state the observation(s) the student should make whilst carrying out this experiment. equation: . observation(s): . (b) Lattice enthalpies give an indication of the strength of ionic bonding. How would the lattice enthalpies of magnesium chloride and calcium chloride differ? Explain your answer. Specimen[2] [3]OCR 2014 H432/01<br />
19 (c) The table below shows the enthalpy changes that are needed to determine the lattice enthalpy of magnesium chloride, MgCl2. Letter Enthalpy change A B C D E F G 1st electron affinity of chlorine 1st ionisation energy of magnesium atomisation of chlorine formation of magnesium chloride atomisation of magnesium 2nd ionisation energy of magnesium lattice enthalpy of magnesium chloride (i) On the cycle below, write the correct letter in each box. Energy / kJ mol1 349 +736 +150 642 +76 +1450 Specimen (ii) Use the BornHaber cycle to calculate the lattice enthalpy of magnesium chloride.OCR 2014 lattice enthalpy =kJ mol1 H432/01 [2] Turn over [3]<br />
20 (d)* Describe and explain the relative reactivity of the halogens, chlorine, bromine and iodine, in their redox reactions with halides, using reactions on a test-tube scale. Include reaction equations and observations in your answer. . . . . . .[6] SpecimenOCR 2014 H432/01<br />
21 BLANK PAGE SpecimenOCR 2014 H432/01 Turn over<br />

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H432/01 Question 19 (a) (b) (c) (i) F B E D FIVE correct FOUR correct THREE correct (cid:57)(cid:57)(cid:57) (cid:57)(cid:57) (cid:57) (ii) 642(+76 + (2150) + 736 + 1450 + (2349) ) (cid:57) 6421864 =2506 (cid:57) (kJ mol1) Mark Scheme June 20XX Marks Mg(s) + 2HCl(aq)MgCl2(aq) + H2(g) (cid:57) Answer is more exothermic than CaCl2 Effervescence AND solid dissolves (cid:57) Lattice enthalpy of MgCl2 (cid:57) because magnesium ion/Mg2+ is smaller (than calcium ions/Ca2+) OR Mg2+ has a greater charge density (than between Ca2+ and Cl) (cid:57) therefore the attraction between Mg2+ and Cl is greater (cid:57) Specimen Guidance State symbols are required ALLOW solid disappears ORA throughout ALLOW charge density here only ALLOW magnesium/Mg is smaller DO NOT ALLOW Mg2+has a smaller atomic radius DO NOT ALLOW chlorine ions DO NOT ALLOW Mg has greater attraction ALLOW attracts with more force for greater attraction but DO NOT ALLOW greater force (could be repulsion) ALLOW IF only one or two correct, award 0 marks. 1450 736 76 642 ALLOW for 1 mark: 2705 (2 x 150 and 2 x 349 not used for Cl) 2356 (2 x 150 not used for Cl) 2855 (2 x 349 not used for Cl) +2506 (wrong sign) DO NOT ALLOW any other answers 13 P M T<br />
H432/01 Question (d)* Mark Scheme June 20XX Answer Marks Guidance Indicative scientific points may include: Trend in reactivityMore shells or increasing radius down the group Increased shielding down the groupMore difficult to gain an electron ObservationsReaction of Cl2 or Br2 with I: orange/brown solution OR purple in organicReaction of Cl2 with Br: yellow solution OR orange in organic Reaction equationsCl2 + 2BrBr2 + 2ClCl2 + 2II2 + 2Cl OR Br2 + 2II2 + 2BrOrder of reactivity linked to observations Please refer to the marking instructions on page 4 of this mark scheme for guidance on how to mark this question. Level 3 (56 marks) Describes and explains concisely the trend in reactivity of the halogens AND Full observations of redox reactions backed up by at least two equations There is a well-developed explanation which is clear and logically structured. The observations and equations are relevant to those trends explained. Clear and confident knowledge of relevant technical language. Level 2 (34 marks) Describes and explains the trend in reactivity of the halogens AND Is able to recall a redox reaction by suitable observations and correctly link to an equation There is an explanation with some structure. The observations and equations are in the most-part relevant to the trend explained. Sound grasp of relevant technical language. Level 1 (12 marks) Describes the trend in reactivity of the halogens with some attempt at explanation AND Is able to recall a redox reaction either by suitable observation or by equation Specimen 14 P M T<br />
H432/01 Question Mark Scheme June 20XX Answer Marks Guidance The information about the trend is basic and communicated in an unstructured way. The information is supported by only observation or equation and the relationship to the trend may not be clear. Basic grasp of relevant technical language 0 marks No response or no response worthy of credit. Total 16 Specimen 15 P M T<br />

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