PHYSICAL SCIENCES: CHEMISTRY PAPER 2
GRADE 12
MEMORANDUM
SENIOR CERTIFICATE EXAMINATIONS
MAY/JUNE 2017

QUESTION 1
1.1 D ✓✓ (2)
1.2 D ✓✓ (2)
1.3 B ✓✓ (2)
1.4 A ✓✓ (2)
1.5 C ✓✓ (2)
1.6 A ✓✓ (2)
1.7 B ✓✓ (2)
1.8 D ✓✓ (2)
1.9 C ✓✓ (2)
1.10 C ✓✓ (2)
[20]

QUESTION 2
2.1 A bond / an atom / a group of atoms ✓ that determine(s) the (physical and chemical) properties of a group of organic compounds. ✓ (2)
2.2
2.2.1 ✓ (1)
2.2.2 Carboxyl (group)✓ (1)
2.3
2.3.1 Ketones ✓ (1)
2.3.2
Marking criteria:

• Functional group ✓
• Two methyl substituents ✓
• Whole structure correct: 3 
                                         3    (3)

2.4
2.4.1 5-bromo-4-ethyl-2,2-dimethylhexane
Marking criteria:

• Correct stem i.e. hexane.✓
• All substituents (bromo, ethyl and dimethyl) correctly identified.✓
• IUPAC name completely correct including numbering, sequence, hyphens and commas. ✓(3)

2.4.2 4-methylpent-2-yne ✓✓
OR
4-methyl-2-pentyne (2)

[13]

QUESTION 3
3.1
3.1.1

(3)

3.1.2 D ✓
Accept:
butan-1-ol (1)
3.1.3 G ✓
Accept
2-methylpropan-2-ol(1)
3.2
3.2.1 (Increase in) chain length / molecular size / molecular mass/ number of C-atoms/ surface area / contact area / number of electrons✓(1)
3.2.2 London forces / dispersion forces / induced dipole forces ✓(1)
3.3
3.3.1 108 (°C) ✓ (1)
3.3.2 Compare compound F with compounds C and D:

• Compound F has a larger molecular mass / molecular size / surface area/contact area / number of C-atoms / number of electrons / than compound C. ✓
• Compound F is more branched than compound D. ✓
• Intermolecular forces in compound F are stronger than in compound C and weaker than in compound D. ✓
• More energy needed to overcome intermolecular forces in compound F than in compound C and less energy needed to overcome (break) intermolecular forces in compound F than in compound D. ✓(4)

3.4

(2)

3.5
3.5.1 Esterification / Condensation ✓(1)
3.5.2

[17]

QUESTION 4
4.1
4.1.1 Addition / hydrogenation ✓(1)
4.1.2 Substitution / halogenation / chlorination ✓(1)
4.1.3 Elimination / dehydration ✓(1)
4.2 2-bromopropane ✓
Note:
IF:
Bromopropane ½
2-bromo✓
propane✓ (2)
4.3
4.3.1 Dehydrohalogenation / Dehydrobromination ✓(1)
4.3.2 Hot✓ ethanolic strong base✓

• Concentrated strong base / NaOH / KOH✓
  OR
  Strong base with no water.
  OR
  Strong base in (pure) ethanol as solvent.
• Strongly heated or hot base
  OR
  High temperature/heat strongly(2)

4.4
4.4.1 H₂O / NaOH / KOH ✓ (1)
4.4.2

(4)
[13]

QUESTION 5
5.1
5.1.1 To measure volume / amount ✓ of gas/oxygen produced.(1)
5.1.2 Catalyst / Speeds up the reaction. / Increases reaction rate. ✓ (1)
5.2 No gas / bubbles produced.✓
OR
Volume of gas in syringe remains constant. / The plunger stops moving.(1)
5.3 CuO / Copper(II) oxide / catalyst ✓ (1)
5.4

• A catalyst provides an alternative pathway of lower activation energy. ✓
• More molecules have sufficient / enough kinetic energy. ✓
  OR
• More molecules have kinetic energy equal to or greater than the activation energy.
  More effective collisions per unit time. / Frequency of effective collisions increases. ✓(3)

5.5
5.5.1 Released ✓
Products at lower (potential) energy than reactant. / Reaction is exothermic / ΔH < 0 ✓ (2)
5.5.2 B ✓ (1)
5.6

(6)
[16]

QUESTION 6
6.1
6.1.1 Products can be converted back to reactants. ✓
OR
Both forward and reverse reactions can take place.(1)
6.1.2 Endothermic ✓ (1)
6.1.3

• K_c increases with increase in temperature. ✓
• Forward reaction is favoured. / Concentration of products increases. / Concentration of reactants decreases. ✓
• Increase in temperature favours an endothermic reaction. ✓(3)

6.1.4 Increases  ✓ (1)
6.1.5 Remains the same  ✓ (1)
6.2
6.2.1

6.2.2 Remains the same✓ (1)
[16]

QUESTION 7
7.1
7.1.1 Weak (acid)✓ (1)
7.1.2 pH = -log[H₃O⁺] ✓
4 ✓ = -log[H₃O⁺]
[H₃O⁺] = 1 x 10^-4 mol∙dm^-3 ✓
(3)
7.2
7.2.1 A substance that produces hydroxide ions / OH- in water. ✓✓
NOTE:
If water is omitted: ½ (2)
7.2.2

Marking guidelines: Formula: c =  n  /n = cV/ ca × Va  = na                       V               Cb × Vb × nb Use mol ratio: 1:1 ✓ Substitution of : 0,16 x 25 /0,16 x 0,025 ✓ Use Vb = 12,5 cm3/0,0125 dm3 ✓ Use 56 g·mol-1 ✓ Substitute V = 0,25 dm3 ✓ Final answer: 4,48 g ✓

(7)
7.2.3 Greater than 7 ✓ (1)
7.2.4 
Due to formation of (OH^-), the solution is basic / alkaline✓

(3)
[17]

QUESTION 8
8.1
8.1.1 Emf ✓(1)
8.1.2 Voltmeter ✓ (1)
8.1.3 Salt bridge ✓ (1)
8.1.4 Temperature : 25 °C / 298 K ✓
Concentration : 1 mol·dm^-3 ✓ (2)
8.2

Examples
Emf increases as concentration (of oxidising agent) increases.
NOTE:
IF:Emf is directly proportional to concentration.½ (2)
8.3

(5)

8.4 Cu²⁺(aq) + Zn(s) ✓ → Zn²⁺(aq) + Cu(s) ✓ Bal. ✓
Accept:

• X²⁺(aq) + Zn(s) → Zn²⁺(aq) + X(s)
• Any metal identified in QUESTION 8.3 of which the ion has a +2 charge.

(3)
[15]

QUESTION 9
9.1 Electrolytic (cell) ✓ (1)
9.2 P ✓ (1)
9.3
9.3.1 Au(s) → Au³⁺(aq) + 3e^- ✓✓
Ignore phases 

(2)
9.3.2 (+)3 ✓ (1)
9.3.3 Electrical energy (is converted) to chemical energy. ✓(1)
9.3.4 Becomes smaller / thinner / eroded / decrease in mass. ✓(1)
9.4 ANY ONE

• Increase in value. ✓
• Protection against rust. (1)

9.5 ANY ONE

• Replace Au³⁺(aq) / electrolyte with Ag⁺(aq) / silver(I) solution / use a silver solution
• Replace P / anode / gold with Ag(s) / silver (1)

[9]

QUESTION 10
10.1
10.1.1 B/air ✓ & C/methane ✓ (2)
10.1.2 Nitric acid / HNO₃ ✓ (1)
10.1.3 A / Sulphur / S ✓ (1)
10.1.4 2NH₃(g) + H₂SO₄ ✓ → (NH₄)₂SO₄ ✓ Bal. ✓ (3)

10.1.5 D / potassium chloride ✓ (1)
10.2
10.2.1

(3)
10.2.2

(3)
[14]

TOTAL: 150