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OCR A Jun 2015 Paper 1 Q2
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![This question is about compounds of Group 3 elements. (a) Aluminium will combine directly with fluorine. Write the equation for the reaction between aluminium and fluorine.[1] (b) Solid aluminium fluoride has a giant ionic lattice structure. (i) Describe what is meant by the term ionic lattice, in terms of the type and arrangement of particles present.[2] (ii) Draw a dot-and-crossdiagram for aluminium fluoride. Show outer electrons only. [2]OCR 2015 Turn over<br />
(c) Solid boron tribromide has a simple molecular lattice structure. The atoms are held together by covalent bonds. (i) What is meant by the term covalent bond ?[1] (ii) Draw a dot-and-crossdiagram to show the bonding in a boron tribromide molecule. Show outer electrons only. (d) State whether the following substances conduct electricity when solid or molten, and explain your answers in terms of the particles involved: [1]aluminium aluminium fluoride boron tribromide. In your answer you should use appropriate technical terms, spelled correctly.[5]OCR 2015<br />
(e) Aluminium has 13 successive ionisation energies. (i) Write the equation for the third ionisation energy of aluminium. Include state symbols.[1] (ii) On the axes below, add crosses to show the 13 successive ionisation energies of aluminium. The value for the first ionisation energy has been completed for you. You do not have to join the crosses. y g r e n e n o i t a s n o 10 11 12 13 ionisation energy number [2] [Total: 15]OCR 2015 Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/OCR_1_QP_JUN15_question_2-0.jpg)
![F321 Question 2 (a) Answer 2Al + 3F2 (cid:198) 2AlF3 (cid:57) (b) (i) Repeating pattern (cid:57) of oppositely charged ions (cid:57) (ii) Al with 8 (or no) outermost electrons AND 3 x fluoride (ions) with dot-and-cross outermost octet (cid:57) Correct charges (cid:57) (c) (i) A shared pair of electrons. (c) (ii) Br x B xBr Br (cid:57) Mark Scheme June 2015 Guidance ALLOW multiples IGNORE state symbols ALLOW regular OR alternating OR uniform (arrangement) for repeating pattern ALLOW positive and negative ions OR aluminium ions and fluoride ions ALLOW oppositely charged ions from a labelled diagram For first mark: If 8 electrons are shown in the cation then the extra electron in the anion must match the symbol chosen for the electrons in the cation IGNORE inner shells IGNORE circles ALLOW one mark if both electron arrangements and charges are correct but only one F is drawn. ALLOW one mark if incorrect symbol is the only error, unless ECF from 2(a) in which both marks are available DO NOT ALLOW any marks for BF3 ALLOW 3[F] 3[F] [F]3 (brackets not required) DO NOT ALLOW [F3] [F3]3 [3F]3 [F]3 Mark<br />
F321 Question (d) Mark Scheme June 2015 Answer Conductivity of Al mark M1: Aluminium conducts in solid and molten states (cid:57) Reason for conductivity of Al mark M2: Aluminium has delocalised electrons (cid:57) Conductivity and reason for molten AlF3 mark M3: Aluminium fluoride conducts when molten AND because it has mobile ions (cid:57) Conductivity and reason for solid AlF3 mark M4: Aluminium fluoride does not conduct when solid AND Solid aluminium fluoride has ions which are fixed (in position) OR ions are held (in position) OR ions are not mobile AND In an (ionic) lattice OR (ionic) structure OR by (ionic) bonds (cid:57) Mark Guidance ALLOW carries charge for conducts IGNORE charge carriers for electrons or ions for M2, M3 and M4. Quality of written communication: delocalis(z)ed spelled correctly and used in context for the second marking point. DO NOT ALLOW M2 if incorrect bonding is seen for Al DO NOT ALLOW ions move for solid Al. IGNORE ions move for molten Al. IGNORE references to aqueous AlF3 for M3 IGNORE delocalised ions OR free ions for mobile ions in M3 DO NOT ALLOW M3 if incorrect bonding is seen in AlF3 DO NOT ALLOW any mention of electrons moving for M3 DO NOT ALLOW suggestion that it is only positive or only negative ions moving for M3 For conductivity parts of M3 + M4 ALLOW AlF3 only conducts when molten ALLOW Solid AlF3 is a poor conductor for M4 ALLOW second and third statements to be unlinked in separate sentences for M4 IGNORE there are no delocalised electrons for M4 DO NOT ALLOW M4 if incorrect bonding is seen in AlF3 Lattice OR structure OR ionic bonds can be seen anywhere in relation to AlF3. ALLOW Solid BBr3 is a poor conductor for M5 ALLOW electrons are fixed in position OR used in bonds<br />
June 2015 Guidance IGNORE there are no delocalised electrons OR there are no free electrons for M5 DO NOT ALLOW M5 if incorrect bonding is seen in BBr3 eg ions are fixed in position ALLOW no (free) ions State symbols required (ignore states on electrons) ALLOW Al2+(g)e (cid:198) Al3+(g) ALLOW e for e IGNORE line if drawn IGNORE 0 if included ALLOW one mark for three lines (no crosses) showing an increase between: first and third; fourth and eleventh; twelfth and thirteenth AND Largest increases between each line ALLOW crosses outside grid F321 Question Answer Mark Scheme Mark Conductivity and reason for BBr3 mark M5 Boron tribromide does not conduct in solid and molten states AND Boron tribromide has no mobile electrons OR no (mobile) ions OR no mobile charge carriers OR no mobile charged particles (cid:57) (i) Al2+(g) (cid:198) Al3+(g) + e (cid:57) (ii) All (thirteen) ionisation energies show an increase (cid:57) The two largest increases are between the third and fourth AND the eleventh and twelfth ionisation energies (cid:57) (e) Total 15<br />](https://learnah.org/wp-content/uploads/2018/08/OCR_1_QP_JUN15_answer_2-0.jpg)
