Physical Sciences Grade 12 P2 North West November 2015 Memo

Downloaded from hlayiso.com Education and Sport Development Department of Education and Sport Development Departement van Onderwys en Sportontwikkeling Lefapha la Thuto le Tihabololo ya Metshameko NORTH WEST PROVINCE NATIONAL SENIOR CERTIFICATE GRADE 12 PHYSICAL SCIENCES: CHEMISTRY (P2) * " SEPTEMBER 2015 : ‘ MEMORANDUM : Sees sees ee eee eee MARKS: 150 This memorandum consists of 17 pages. Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 2 NW/September 2015 NSC — Memorandum GENERAL GUIDELINES 1. CALCULATIONS 1 1.2 1.3 1.4 1.5 1.6 1.7 Award marks for: correct formula, correct substitution and correct answer with unit. Do not award any marks if an incorrect or inappropriate formula is used, even though there may be relevant symbols and applicable substitutions. When an error is made during substitution into a correct formula, award a mark for the correct formula and for the correct substitutions, but do not give any further marks. If no formula is given, but all substitutions are correct, the candidate forfeits one mark. Example: No K, expression, correct substitution: =O ve ov 2. “oa” * ? G Marks are only awarded for a formula if a calculation has been attempted, i.e. substitutions have been made or a numerical answer is given. Marks can only be allocated for substitutions when values are substituted into formulae and not when listed before a calculation starts. All calculations, when not specified in the question, must be done correctly to TWO decimal places. 2. DEFINITIONS Award TWO marks for a correct definition. Do not award any marks for an incorrect or partially correct definition. 3. UNITS 3.1 3.2 Candidates must be penalised only once for the repeated use of an incorrect unit within a question or subquestion. Units are only required in the final answer of a calculation. Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 3 NW/September 2015 NSC — Memorandum 3.3. Award marks for an answer only and not for a unit per se. Candidates forfeit the mark allocated for the answer in each of the following situations: - Garrect answer + wrong unit - Wrong answer + correct unit - Correct answer + no unit 3.4 Separate compound units with a multiplication dot, not a full stop, for example, mol:dm’. Accept mol.dm® (or mol/dm*) for marking purposes. 4, GENERAL 4.1 _ If one answer or calculation is required, but the candidate gives two, mark only the first one, irrespective of which one is correct. If two answers are required, mark only the first two, etc. 4.2 When achemical FORMULA is asked, and the NAME is given as answer, the candidate forfeits the marks. The same rule applies when the NAME is asked and the FORMULA is given. 4.3. When redox half-reactions are to be written, the correct arrow should be used. If the equation HS +S+2H*+20 (34) is the correct answer, the marks must be given as follows: HS =S+2H*+2e (4) HS —S+2H*+2e (%) S + 2H’ +2e —H,S (%) S +2H* + 2e = HS (%) 4.4 When candidates are required to give an explanation involving the relative strength of oxidising and reducing agents, do not accept the following: Stating the position of a substance on table 4 only (e.g. Cu is above Mg). Using relative reactivity only (e.g. Mg is more reactive than Cu). The correct answer would be for instance: Mg is a stronger reducing agent than Cu and therefore Mg will be able to reduce Cu** ions to Cu. The answer can also be given in terms of the relative strength as electron acceptors and donors. Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 4 NW/September 2015 45 46 4.7 4.8 4.9 4.10 NSC — Memorandum One mark is forfeited when the charge of an ion is omitted per equation. The error carrying principle does not apply to chemical equations or half reactions. For example, if a learner writes the wrong oxidation/reaction haif- reaction in the subquestion and carries the answer to another sub-question (balancing of equations or calculation of E:.,) then the learner must not be credited for this substitution. In the structural formula of an organic molecule all hydrogen atoms must be shown. Marks must be deducted if hydrogen atoms are omitted. When a structural formula is asked, marks must be deducted if the learner writes the condensed formula. When an IUPAC name is asked and the candidate omits the hyphen (e.g. instead of pent-1-ene or 1-pentene the candidate writes pent 1 ene or 1 pentene), marks must be forfeited. When a chemical reaction is asked, marks are awarded for correct reactants, correct products and correct balancing. If only a reactant(s) followed by an arrow, or only a product(s) preceded by an arrow is/are written, marks may be awarded for the reactant(s) or product(s). If only a reactant(s) or only a product(s) is written without an arrow, no marks are awarded for the reactant(s) or product(s). Example: No + 3H2v —» 2NHs” bal. W No + 3H, —»¥ 1/3 —> NH3Y 1/3 No + 3He 0/3 NH3 0/3 5. POSITIVE MARKING Positive marking regarding calculations is followed in the following cases: 5.1 Subquestion to subquestion: When a certain variable is calculated in one subquestion (e.g. 3.1) and needs to be substituted in another (3.2 or 3.3), e.g. if the answer for 3.1 is incorrect and is substituted correctly in 3.2 or 3.3, full marks must be awarded for the subsequent subquestions. Copyright reserved Please turn over

Downloaded from hlayiso.com The correct option is B

Downloaded from hlayiso.com Physical Sciences/P2 6 NW/September 2015 NSC — Memorandum 2.4 H oH H “Ty —H —> 1 ain + /\ H H 4H H H H H H vv mn ()) 2.5 2.5.1. Dehydration ¥ (1) 2.5.2 Propenev (1) 2.6 2.6.1 Propan-2-one vv (2) 2.6.2 Aldehydes ¥ (1) [15] QUESTION 3 3.1 3.1.1. Functional group v (1) 3.1.2 Melting point. v (1) 3.1.3 Number of C-atoms (All have single bonds). v (1) 3.2 Carboxylic acid vv (2) 3.3 CnHan+2 Vv (2) 3.4 Melting points increases from A-C. vv (2) 3.5 Compound A has weak Van der Waal’s forces (London forces) whilst B and C have strong hydrogen bonds between their molecules.v Hence, less energy is needed to break the weak intermolecular forces in A than in B and C.v Compound B has one site of hydrogen-bonding whilst compound C has two sites of H-bonding.v Thus, C has stronger intermolecular forces between its molecules than B,“ hence more energy is needed to overcome the intermolecular forces in C than in B. “ (5) [14] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 7 NW/September 2015 NSC ~ Memorandum QUESTION 4 4.144 H i H—C——-c— Br H——C—H I H vv (2) 4.1.2 | i n—bow H-——C——H a 4 v v v H:0 | Hi ——-C——Br + KOH Hi i c fo] H + KBr H H H—C——H H—C——H | | H H (3) 4.1.3 Ethanol as solvent” / NaOH(aq) Yor KOH(aq) / Mild heat (2) 4.1.4 Hydrolysis / Substitution reactionv “ (2) 4.2.1. Condensation polymer is a polymer formed by two monomers with different functional groups that are linked together in a condensation reaction in which a small molecule (usually water) is lost. (2) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 8 NW/September 2015 NSC — Memorandum H cl \ —o” 4 oN 4.2.3. Chloroethylene /Chloroethene/Vinyl chloride. vv 4.3.1. Condensation polymer “ 4.3.2 Addition polymer “ 4.4 ANY of the following: - Blood transfusion sets”; - Transparent food packaging trays; ~ Plumbing pipes; - Synthetic leather, etc. QUESTION 5 5.1 An acid is a proton donor. v “ 5.2 5.2.1 H2O0 v 5.2.2 H,0* v 5.3 5.3.1 lonises / dissociates completely (in water) Vv v §.3.2 pH =-log [H30*] Ratio: 1:2 0,025 mol H3SO4 —»0,05 mol H30* “ PH = -log [Hs07] ¥ = -log [0,05] “ =1,3¥ 5.4 5.41 OH Vv 5.4.2 DECREASE v Copyright reserved Please turn over (2) (2) (1) (1) (1) [18] (2) (1) (2)

Downloaded from hlayiso.com Physical Sciences/P2 9 NW/September 2015 NSC — Memorandum 5.5 — n(H2SO4) = cV Y = (0,4)(15x10°) v = 6x10 mol ¥ n(NaQH) = cV— = (0,2)(25x10°) v = 5x10° mol From the balanced equation: 4 mol of HoSO, =2 mol of NaOH Hence, n(NaOQH) needed to neutralise the acid = 2(6x10°°) =12x10° mol ¥ Therefore insufficient NaOH was added to the acid since 5x10° mol is less than the required 12x10 mol ¥ (6) [18] QUESTION 6 6.1. What is the relationship between the reaction surface or state of division of a solid and the rate of a reaction? / How does reaction surface (or state of division) influence the rate of a chemical reaction? v v OR What is the relationship between the reaction surface (of a reactant) and the time that reaction takes to progress completely? (2) 6.2 CaCOa,(s) + 2HCl(aq) v —» CaClo(aq) + H20(I) + CO2(g) “ bal ¥ (3) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 6.3 10 NW/September 2015 NSC — Memorandum GRAPH OF DECREASE IN MASS VERSUS TIME 2,0¢ im TOS TTY 1,5 1,0 y Decrease in mass (g) 0,5 6 8 Time (min) CHECKLIST MARK ALLOCATION Heading v Correct scale on both axes Correct labelling of both axes Plotting of points Vv Correct shape of curves 6.4 Reaction A is faster than Reaction BY 6.5 The same (2g) v 6.6 The greater the reaction surface, the higher the rate of reaction will be.v “ Copyright reserved Please turn over (6) (1) (1) (2) [15]

Downloaded from hlayiso.com Physical Sciences/P2 11 NW/September 2015 NSC — Memorandum QUESTION 7 7.1 Le Chatelier’s principle: When the equilibrium in a closed system is disturbed, the system will re-instate a new equilibrium by favouring the reaction that will oppose the disturbance. OR Le Chatelier’s principle: When conditions (concentration, temperature and pressure) are changed in equilibrium in a closed system, equilibrium is shifted to the side which opposes the change. (2) 7.2. OPTION 1: CALCULATION USING CONCENTRATION 1 He 1cO 1H20 1cO Initial x/10 0,03 0 0 concentration Reacted/produced | 0,02 0,02 0,02 v 0,02 v Equilibrium X/10 - 0,02 | 0,01 0,02 0,02 v Ke [CO]LH,O} v No Ke expression, correct [H,][CO,] substitution Max. 7/8 (0,02)(0,02) y Wrong Kc expression 4v = Max. 4/8 X/10 ~0,02)(0,01) ax X = 0,3 n(H2) = 0,3 mol v OPTION 2: CALCULATION USING NUMBER OF MOLES 1H 1CO. | 1H,0 1co0 Initial quantity (mol) X 0,3 0 ie) Change (mol) -0,2 -0,2 0,2 0,2 | Mole tatio ~ Quantity at equilibrium (mol) X-0,2 O41 027% (02 |v Equilibruim concentration X-0,2 0,01 0,02 0,02 | Divide (mol.dm’?) 10 by 10 v [COMH,O] [H, CO, ] av = —(0,02)(0.02) X/10 -0,02)(0,01) X = 03 Thus n(H2)= 0,3 mol ¥ (8) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 12 NW/September 2015 NSC — Memorandum 7.3. -ve marking Exothermic “ A decrease in K, value at a higher temperature implies the reverse reaction (endothermic)/ the reaction that uses energy is favoured. V Results in lower product concentration (less products) OR higher reactant concentration (more reactants). v Equilibrium position shifts to the right/ lies to the right. “ (4) [14] QUESTION 8 8.1 - Temperature of 25°C v - Concentration of 1mol'dm® v (2) 8.2 Ag*(aq)+ @& — Ag(s) vv (2) 8.3 Ni v (1) 8.4 The emf decreases. v (1) 8.5 Ni(s) + 2Ag*(aq) “ — Ni**(aq) + 2Ag(s). Vv (3) 8.6 Ni-Ni**+2e mol ratios: from the balanced equation is 02: 02 : 0,4 m=n(Ni).M % =0,2x59v = 11,8g of Ni is lost from the anode. “ (3) 8.7 A -ve marking Second (2") or B. Y Magnesium (Mg) is a better reducing agent than Nickel (Ni) and its potential difference is -2,36 V whilst that of Ni is -0,27 V. v Silver (Ag) has the same oxidising ability in both galvanic cells. “ (3) [15] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 13 NW/September 2015 NSC ~ Memorandum QUESTION 9 9.1. The process in which electricity is used to bring about a chemical change in an electrolytic cell/ decompose /break compounds into components. “” OR A process in which electrical energy is converted to chemical energy. (2) 9.2 Pv’, itis the positive electrode/ anode. “ Oxidation takes place at the positive electrode /anode. “ (3) 9.3 Cu(aq)+2e — Cus) vv (2) 9.4 The rate at which copper is oxidised (at the anode) is equal to the rate at which copper ions are reduced (at the cathode). v “ Rate of oxidation equals ihe rate of reduction. (2) 9.5 -Ornaments v; Electrical conductors v/Jewellery in QUESTION 10 10.1 4NHa(q) +5 O2(aq) ~—» 4NO(g) + 6H2O(g) v ¥ (3) 10.2 Ptor Platinum ¥ (1) 10.3. Catalytic oxidation of NH3 VW” (2) 10.4 HNO ¥ (1) 10.5 Ostwald (process). v (1) 10.6 - Brown or yellow scorching around the edges of the leaves. “” - Flowers become dull and sparse. “ - Fruit yield low and of poor quality. (2) [10] TOTAL: 150 Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 14 NW/September 2014 NSC — Memorandum PHYSICAL SCIENCES GRADE 12 PAPER 2 ANALYSIS 2015 Knowledge Taxonom area . ay 4 7) 2:3 n a 5 zo a 7) é = Zo 3a} O38 az} o/2 z Og og ac Fea ze]/ zZzj/H] ww] 2 © we as zs Spo wu] 1/5) ¥] & 8 “¢ 2% <6 3827]s/ &] Si=] Sl e& 3 wi § ug pH) st Siz] 3/9/28] = ry og 6 Ze a aja § = a fo} wos 10 & tig J 2 6 uz a2 ES a Fla! Zio}] E] g S41 =8 ge RSG wl eiz] eo} 3 fe) on Py wt 2 EE] #/@]) Fl so z ° Zz Ess 3/515 g o Bes = a >2°o oF 5 Content E|M/D M;D|E;]MjiD Mj}D Marks 71 | MOLECULAR : STRUCTURES 2 2 PHYSICAL 1.2 | properties 2 2 2 RATE OF 1.3 | REACTION 2 2 2 TYPES OF 1.4 | Reactions 2 2 2 ACID-BASED 1.5 | REACTION 2 2 2 TYPES OF 1.6 | REACTIONS 2 2 2 REDOX 1.7 | REACTION 2 2 2 RATE OF 1.8 | REACTION 2 2 2 CHEMICAL 1.9 | Equivisrium 2 2 2 ACIDS AND 1.10 | Bases 2 2 | 20 2.1 ISOMERS 2 2 2 2.2 | isomers 2 2 STRUCTURAL 2.3.1 | FORMULAE 2 2 2 ORGANIC 2.3.2 | Propuct 1 1 ul TYPE OF 2.4 | REACTION 3 3 3 STAUCTURAL 2.5.1 | FORMULAE 1 1 1 STRUCTURAL 2.5.2 | FORMULAE 1 1 1 2.6.1 | IUPAC NAMING 2 2 2 HOMOLOGOUS 2.6.2 | sens 1 1 1 | 1 PHYSICAL 3.1.1 | properties _| 1 1 1 PHYSICAL 3.1.2 | properties | 1 1 1 PHYSICAL 3.1.3 | PROPERTIES 1 1 1 HOMOLOGOUS 3.2 __| series 2 2 GENERAL 3.3 | FORMULAE 2 2 2 PHYSICAL 3.4 _| PROPERTIES 2 2 2 INTERMOLECU 3.5 _| LAR FORCES 5 5 5 | 14 Copyright reserved

Downloaded from hlayiso.com Physical Sciences/P2 Content E|M NSC - Memorandum 15 D NW/September 2015 Marks 414 STRUCTURAL 2 FORMULAE 4.1.2 STRUCTURAL FORMULAE 4.1.3. REACTION CONDITIONS nN 4.1.4 TYPE OF 2 REACTION 4.2.1 POLYMERS 2 4.2.2 POLYMERS 4.2.3 POLYMERS MyMPNy MIM {|My [MY jw [hy 4.3.1 POLYMERS — 4.3.2 POLYMERS 4.4 POLYMERS a 18 5.1 ACIDS & BASES 5.2.1 ACIDS & BASES = jp §.2.2 ACIDS AND BASES — 5.3.1 ACIDS & BASES 5.3.2 ACIDS AND BASES 5.4.1 ACIDS & BASES 5.4.2 ACIDS & BASES 5.5 ACIDS & BASES 18 6.1 RATE OF REACTION 6.2. BALANCING REACTIONS 6.3 GRAPHS INTERPRETATI ONS 6.4 RATE OF REACTION 6.5 REDOX REACTIONS 6.6 RATE OF REACTION 15 7A APPLICATION OF EQUILIBRIUIM 7.2, APPLICATION OF EQUILIBRIUM 7.3. APPLICATION OF EQUILIBRIUM 14 8.1 ELECTROCHE- MICAL REACTIONS 8.2 ELECTROCHE- MICAL. REACTIONS Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences/P2 16 NSC ~ Memorandum NW/September 2014 8.3 ELECTROCHE- MICAL 1 REACTIONS 8.4 ELECTROCHE- MICAL REACTIONS 8.5 ELECTROCHE- MICAL REACTIONS 8.6 ELECTROCHEMI STRY (APPLICATION ) 8.7 ELECTROCHEMI STRY {APPLICATION ) wo 15 9.1 ELECTROLYSIS 9.2 ELECTROLYTIC CELLS 9.3 ELECTROLYTIC CELLS 9.4 ELECTROLYTIC CELLS 9.5 ELECTROLYTIC CELLS NO] mlm] o] wy 11 10.1 ELECTROCHEMI CAL CELL w IN IS |S [wo [hw 10.2 ELECTROCHEMI CAL CELL ae 10.3 ELECTROCHEMI 2 CAL CELL 10.4 ELECTROCHEMI 1 CAL CELL —~{ Mls o 10.5 ELECTROCHEMI CAL CELL 10.6 FERTILISERS 2 10 ACTUAL MARKS 18% % ACHIEVED EXPECTED MARKS ae 36% ee 9% Overall Easy Medium Difficult ACTUAL MARKS 34 68 48 23% % ACHIEVED 45% 32% EXPECTED 30 MARKS ca 40 30 Copyright reserved 60% 7% 100%