Technical Sciences Grade 12 P2 GP Prelim 2023 Memo (English)

Downloaded from hlayiso.com PREPARATORY EXAMINATION 2023 MARKING GUIDELINES TECHNICAL SCIENCES (PAPER 2) (11102) 5 pages

Downloaded from hlayiso.com 11102/23 QUESTION 1 1.1 B ✓✓ (2) 1.2 B ✓✓ (2) 1.3 B ✓✓ Award 2 mark (2) 1.4 D ✓✓ (2) 1.5 C ✓✓ (2) 1.6 D ✓✓ (2) [12] QUESTION 2 2.1 Homologous series is a series of organic compounds that can be described by the same general formula and where each member differs from the next by a CH2-group. ✓✓ (2) 2.2 2.2.1 E✓ (1) 2.2.2 C✓ (1) 2.2.3 D✓ (1) 2.2.4 A & F ✓✓ or nothing (2) 2.3 2.3.1 H H O H H | | || | | H–C–C–O–C–C–C–H | | | | H H H H Ester ✓ Correct carbon structure ✓ Correct number and positions of H ✓ (3) 2.3.2 H H H H O | | | | || H – C – C– C – C – C – O – H Or Pentenioc acid | | | | H H H H Carboxylic acid ✓ Correct carbon structure ✓ Correct number and positions of H ✓ Accept structural formula (3) [13] 2

Downloaded from hlayiso.com 11102/23 QUESTION 3 3.1 Boiling point is the temperature at which the vapour pressure equals atmospheric pressure. ✓✓ (The stronger the intermolecular forces, the higher the boiling point) (2) 3.2 Compound C has a longer carbon chain than compound B ✓ and compound B has a longer carbon chain than compound A. ✓ OR Different in carbon chain OR Chain length increase frm A to C (2) 3.3 Both compounds have (London)- and dipole-dipole forces, ✓ but compound C has a longer carbon chain than compound A, which means compound C has stronger London forces, ✓ more energy is needed to overcome these intermolecular forces. ✓ (3) 3.4 A✓ (1) 3.5 Compound A has the weakest intermolecular forces because it has the shortest carbon chain, ✓ less energy is needed to overcome these intermolecular forces ✓✓ OR Vapour pressure is inversely proportional to boiling point, ✓the higher Vapour pressure the lower the melting point or boiling point✓✓ (3) [11] QUESTION 4 4.1 Addition ✓ (1) 4.2 H2O or Water ✓ (1) 4.3 H H | | H–C–C–H | | H O – H ✓✓ (2) 4.4 Hydrohalogenation ✓ /Addition (1) 4.5 Bromoethane ✓✓ (2) 4.6 2C2H6 + 7O2 → 4CO2 + 6H2O Marking Criteria: • Reactants ✓ • Products ✓ • Balancing ✓ (3) 3

Downloaded from hlayiso.com 11102/23 [10] QUESTION 5 5.1 An intrinsic semiconductor is a pure semiconductor. ✓✓ (2) 5.2 Metalloids ✓/Semi-metal/ Semi-conductor (1) 5.3 ✓✓ (2) [5] QUESTION 6 6.1 Electrolytic ✓ (1) 6.2 Battery/cell/power source/two electrodes are in the same container ✓ (1) 6.3 Electroplating ✓ (1) 6.4 P (Anode) is made up of an active copper electrode and Q (cathode) is made up of an inactive carbon electrode (unreactive) ✓/ Any relavent response (1) 6.5 Decoration/to prevent corrosion/ to increase appearance/Any relavent response (1) 6.6 Chloride ion (Cl-) (1) 6.7 Cu2+ + 2e- → Cu ✓✓ (2) 6.8 Chlorine gas/Cℓ2 (1) 6.9 Decreases ✓ Cℓ─ is oxidised to Cℓ2 ✓and Cu2+ is reduced to Cu. ✓ OR Cℓ changes to Cℓ2 ✓ and Cu2+ changes to Cu. ✓ ─ (3) [12] 4

Downloaded from hlayiso.com 11102/23 QUESTION 7 7.1 An electrochemical cell that converts the chemical energy into electrical energy ✓✓ (2) 7.2 Pressure applies to gases./There is no gas. ✓ (1) 7.3 Eθcell = Ereduction θ − Eθoxidation ✓ Note: = +0,34✓ – (-0,76) ✓ Accept any other correct formula from the = +1,1 V ✓ data sheet. Any other formula using unconventional abbreviations, e.g., Ecell = EOA – ERA Followed by correct substitutions: Max. 2 3 (4) 7.4 Zn → Zn2+ + 2e- Cu2+ + 2e- → Cu Marking criteria: Zn + Cu2+✓ → Zn2+ + Cu ✓✓ Reactants✓ Products✓ Balancing✓ (3) 7.5 No, ✓ emf of the bulb is greater than emf of the cell. ✓ OR Reaction rate does not provide enough current/ energy✓ (2) [12] TOTAL: 75 5