Physical Sciences (chemistry)
Paper Two (P2)
Grade 12
Amended Senior Certificate Exam
Past Papers And Memos May/june 2016

MEMORANDUM

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

[20] 

QUESTION  2  
2.1  

2.1.1 E ✓ (Accept: methyl propanoate) (1) 
2.1.2 C ✓ (Accept: butan-1-ol) (1) 
2.1.3 D ✓ (Accept: 2,2-dimethylpropane) (1) 

2.2  

2.2.1 Pent-2✓-yne✓        OR            2✓-pentyne✓ (2)  

2.2.2  
 (2)

2.2.3 2-methylbut-1-ene       OR       3-methylbut-1-ene 
Accept      2-methyl-1-butene   (3)

2.3  

2.3.1 Esters ✓ (1) 
2.3.2 Sulphuric acid/H₂SO₄ ✓ (1)  
2.3.3 Methyl✓ propanoate ✓ (2)  

[14]  

QUESTION 3  
3.1 The temperature at which the vapour pressure equals the atmospheric  pressure (external pressure). ✓✓ (2 marks or no marks)  
3.2 

Examples:

• Boiling point increases with increase in number of (C) atoms/chain length/  molecular size/molecular mass. 
• Boiling point decreases with decrease in number of C atoms/chain length/  molecular size/molecular mass. 
• Boiling point is proportional to number of C atoms/chain length/molecular  size/molecular mass.  (2)  

3.3  

3.3.1 P ✓ (1) 
3.3.2 R ✓ (1) 

3.4 ∙       

• Between alkane molecules are London forces/dispersion forces/induced  dipole forces.  ✓
• In addition to London forces and dipole-dipole forces each alcohol  molecule has (one site) for hydrogen bonding. ✓
• In addition to London forces and dipole-dipole forces each carboxylic acid  molecule has two sites for hydrogen bonding. ✓ (Accept: more  sites) 
• Intermolecular forces in carboxylic acids are stronger than intermolecular  forces in alkanes and alcohols./Intermolecular forces between alkane and  alcohol molecules are weaker than intermolecular forces between  carboxylic acid molecules.✓ 
• More energy is needed to overcome/break intermolecular forces in  carboxylic acids than in the other two compounds. ✓  (5) 

[11]  

QUESTION 4  
4.1  

4.1.1 Addition/Hydrogenation ✓  (1)  
4.1.2 Elimination/Dehydrohalogenation/Dehydrobromination ✓  (1)  
4.1.3 Substitution/Halogenation/Bromination ✓  (1)  

4.2  

4.2.1 Pt/Ni/Pd/platinum/nickel/palladium ✓ (1)  
4.2.2 H₂SO₄/H₃PO₄/sulphuric acid/phosphoric acid ✓ (1) 
4.2.3 Hydration ✓ (1)  
4.2.4 2✓-bromopropane ✓ (2) 

4.3  
              (5)  

4.4 ∙ 

• Higher temperature ✓
• Concentrated base/Base dissolved in ethanol ✓  (2) 

[15]  

QUESTION 5  
5.1 ANY TWO:  

• Temperature (of reaction mixture)✓
• (Addition of a) catalyst ✓
• Concentration (of reactants) (2) 

5.2 Sulphur/S ✓ (1) 
5.3 Water is used to dilute/change the concentration (of the Na₂S₂O₃(aq)) ✓ (1)  
5.4 

Dependent variable: rate (of reaction)/(reaction rate)  
Independent variable: concentration
Examples: 

• What is the relationship between concentration and reaction rate? 
• How does the reaction rate change with change in concentration?  (2) 

5.5 A ✓ (1)  
5.6 Experiment B: 

•  The concentration of Na₂S₂O₃(aq) is higher./More Na₂S₂O₃ particles per  unit volume. ✓Accept: higher volume of Na₂S₂O₃(aq) is used 
• More particles with correct orientation  ✓
• More effective collisions per unit time / Higher frequency of effective  collisions. ✓
  OR

Experiment D:  

• The concentration of Na₂S₂O₃(aq) is lower./Less Na₂S₂O₃ particles per  unit volume. ✓
• Less particles with correct orientation.✓
• Less effective collisions per unit time./Lower frequency of effective  collisions. ✓  (3) 

5.7

QUESTION 6 
6.1 Reversible reaction ✓ (1)  
6.2 Endothermic ✓   →      ∆H is positive./∆H > 0/(Net) energy is absorbed./More energy is absorbed  than released/Energy of product > energy of reactant. ✓  (2)  
6.3 Larger than ✓      →    K_c > 1 ✓ (2)  
6.4 (9)  

OPTION 1 
n = ^m/_M
= ¹⁶⁸/₂₈
= 6 mol  

Kc =     [CO]²
           [CO²]✓
14 ✓ =        (3)²
                  x − 3
                    2 

∴x = 4,29 mol ✓

OPTION 2  
n = ^m/_M                                                                         c = n/v
= ¹⁶⁸/₂₈                                                              = ^6/₂ (divide by 2)          
= 6 mol                                                                 = 3 mol.dm^-3 

Kc =     [CO]²
           [CO₂]✓
14 ✓ =        (3)²
                x −1,5

∴x = 2,14 mol·dm^-3

 n(CO₂) = cV 
 = (2,14)(2)  

= 4,29 mol ✓ 

 OPTION 3 
n = ^m/_M
= ¹⁶⁸/₂₈
= 6 mol  

Kc =     [CO]²
           [CO₂]✓
14 ✓ =        (3)²
                [CO₂]✓
∴ [CO₂] = 0,64 mol·dm^-3  

6.5  

6.5.1 Remains the same ✓ (1) 
6.5.2 Decreases✓ (1)  
6.5.3 Increases✓ (1)  

[17]  

QUESTION 7  

7.1  

7.1.1 An acid is a proton/ H⁺ donor. ✓✓ NOTE: not H₃O+ (2 or/of 0)  (2)  
7.1.2 H₂O ✓ 
         H₂CO₃ ✓ (2) 

7.1.3 H₂O ✓     OR/OF     HCO^-₃ (1)  

7.2  

7.2.1
       (8)  

7.2.2 POSITIVE MARKING FROM QUESTION 7.2.1  (4)  

[17] 

QUESTION 8  
8.1 Electrons are transferred. ✓ OR/OF The oxidation number of Mg/H changes.  OR/OF Mg is oxidised / H⁺ is reduced.   (1) 
8.2 H+ ions/HCℓ/H+(aq)/HCℓ(aq) ✓ (1)  
8.3 Ag is a weaker reducing agent ✓(than H₂) and will not be oxidised ✓to Ag⁺ ✓ OR/OF H₂ is a stronger reducing agent ✓ (than Ag) and will be oxidised ✓ to H⁺.✓           (3) 
8.4 Electrode/Conductor of electrons (in hydrogen half-cell) ✓  (1)  

8.5  

8.5.1  Chemical energy to electrical energy ✓ (1)  
8.5.2 Provides path for movement of ions./Completes the circuit./Ensures electrical  neutrality in cell. ✓ (1)  
8.5.3 2H⁺ + 2e^- → H₂ ✓✓  (2) 

8.5.4 Mg(s) | Mg²⁺(aq) || H⁺(aq) | H₂(g) | Pt  ✓ ✓ ✓     OR/OF Mg(s) | Mg²⁺(1 mol·dm^-3) || H⁺(1 mol·dm^-3) | H₂(g) | Pt  
Accept
Mg | Mg²⁺ || H⁺ | H2 | Pt (3)

8.6 (4)  

8.7 Increases✓ (1)  

[18] 

QUESTION 9  

9.1  

9.1.1 Electrolyte✓ (1) 
9.1.2 Electrolytic (cell) ✓ 
          Electrolysis ⁰/1   (1) 

9.2 A to/na B ✓ (1) 
9.3  

9.3.1 B ✓(1)  
9.3.2  A ✓(1)  

9.4 Decreases ✓     Copper (Cu) is oxidised to Cu²⁺/Oxidation takes place at A/Electrons are lost.  ✓ 

  [7]  

QUESTION 10
10.1  

10.1.1 Air ✓ (1)  
10.1.2 Natural gas/methane/oil/coal ✓ (1)  
10.1.3 Sulphur/iron pyrite/Iron sulphide ✓   (1)  

10.2  

10.2.1 Haber ✓ (1) 
10.2.2 Ammonia✓ (1) 
10.2.3 H₂SO₄ ✓ (1) 
10.2.4 SO₃+ H₂SO₄ ✓→ H₂S₂O₇ ✓ Bal. ✓ (3) 

10.3  

10.3.1 %N[NH₄NO₃] = ²⁸/80  ✓ x 100 = 35%  
           %N[(NH₄)₂SO₄] = ²⁸/132 ✓ x 100 = 21,21%  
Ammonium nitrate (has the highest percentage of nitrogen) ✓  (4)  

10.3.2 Ostwald (process) ✓ (1)  

[14]  
TOTAL: 150