PHYSICAL SCIENCES
PAPER 2
GRADE 12 
NSC EXAMS
PAST PAPERS AND MEMOS JUNE 2019

INSTRUCTIONS AND INFORMATION

1. Write your full NAME and SURNAME in the appropriate spaces on the  ANSWER BOOK.
2. This question paper consists of SEVEN questions. 
3. Start EACH question on a NEW page in the ANSWER BOOK.
4. Number the answers correctly according to the numbering system used in  this question paper.
5. Leave ONE line between two sub-questions, for example between  QUESTION 2.1 and QUESTION 2.2.
6. You may use a non-programmable calculator.
7. You may use appropriate mathematical instruments.
8. You are advised to use the attached DATA SHEETS.
9. Show ALL formulae and substitutions in ALL calculations.
10. Round off your FINAL numerical answers to a minimum of TWO decimal  places. 
11. Give brief motivations, discussions, et cetera where required.
12. Write neatly and legibly.

QUESTIONS 

QUESTION 1: MULTIPLE-CHOICE QUESTIONS 
Four options are provided as possible answers to the following questions. Each  question has only ONE correct answer. Write only the letter (A–D), corresponding  to the correct answer of your choice, next to the question number (1.1–1.10) in  the ANSWER BOOK, for example 1.11 D. 
1.1 Which ONE of the following compounds has a DOUBLE BOND in its  structure? 

1. Ethane
2. Ethene
3. Polyethene 
4. Bromoethane (2)

1.2 By definition the boiling point of a liquid is the temperature at which … 

1. a liquid changes to vapour.
2. the vapour pressure equals atmospheric pressure. 
3. the vapour pressure is less than the atmospheric pressure.
4. the vapour pressure is greater than the atmospheric pressure. (2) 

1.3 Which ONE of the following is the CORRECT IUPAC name of the  compound shown below? 

1.  2-bromobutane
2. 2-methyl-2-bromopropane 
3. 2-bromo-2-methylpropane
4. 2,2,2-trimethylbromomethane (2)

1.4 Consider the reaction represented by the equation below: 
CH₃Br + H₂O → CH₃OH + HBr  
The TYPE of reaction shown above is … 

1. substitution. 
2. combustion. 
3. esterification. 
4. polymerisation. (2) 

1.5 The boiling points of propanal and propanone are compared.  
Which ONE of the following is the INDEPENDENT variable in this  comparison? 

1. Molar mass 
2. Chain length 
3. Hydrogen bonds 
4. Homologous series (2) 

1.6 Which ONE of the following factors will change the value of the  equilibrium constant, Kc? 

1. Pressure 
2. Surface area 
3. Temperature 
4. Concentration (2) 

1.7 The reaction of magnesium powder and hydrochloric acid is used to investigate the factors that affect reaction rate. The balanced equation for  the reaction is: 
Mg(s) + 2HCℓ (aq) → MgCℓ₂(aq) + H₂(g) 
In ALL the experiments the hydrochloric acid is in EXCESS and the magnesium powder is completely covered. 
The results of the experiments are shown in the table below: 

Which experiments will produce the SAME amount of hydrogen at same  temperature and pressure? 

1.  P and Q
2. Q and R
3. R and S 
4. P and S (2)

1.8 Diluted hydrochloric acid is spilt on floor tiles in the laboratory. Which ONE of the following substances can be used to neutralise the acid? 

1. NaCℓ 
2. NH₄Cℓ 
3. H₂SO₄ 
4. Na₂CO₃ (2)

1.9 Study the ionisation reactions given below: 

H₃PO₄ + H₂O → H₂PO₄^- + H₃O⁺ 
H₂PO₄^- + H₂O → HPO₄^2- + H₃O⁺ 

In the reactions H2O acts as a(n) … 

1. base. 
2. ampholyte. 
3. weak acid. 
4. strong acid. (2) 

1.10 The potential energy diagram shown below is for the reversible  hypothetical reaction shown below: 

            2 AB(g) ⇌ A₂B₂(g) 

Consider the following statements about the reaction: 

1. The forward reaction is endothermic 
2. The value of ΔH for the REVERSE reaction is equal to q
3. The activation energy for the reverse reaction is equal to p + q Which of the above statements is/are TRUE? 
   1. I only
   2. I and II 
   3. III only 
   4. II and III (2) [20] 

QUESTION 2 
A test tube containing an alcohol P, carboxylic acid R and sulphuric acid is  heated in a water bath, as illustrated below. A piece of wet cotton wool is placed  at the mouth of the test tube. 

Alcohol P + Carboxylic acid R Ester + X 

2.1 Is the sulphuric acid that is used CONCENTRATED or DILUTE? (1)
2.2 What is the purpose of placing cotton wool at the mouth of the test tube? (1)
2.3 Write down the molecular formula of the inorganic product, X. (1)
2.4 Alcohol P is a positional isomer of propan-2-ol. Write down the IUPAC name of alcohol P. (2) 
2.5 Chemical analysis shows that carboxylic acid R contains 54,55% C,  9,1% H and x % O. The molar mass of the ester produced is 130 g·mo^l-1. Determine by calculation the MOLECULAR formula of carboxylic acid R. (8) [13]

QUESTION 3 
3.1 The boiling points of three compounds (A, B and C) are compared in  the table below: 

3.1.1 For compound C write down the: 

1.  Name of the homologous series to which it belongs (1)
2. STRUCTURAL formula (2)

3.1.2 Give a reason why this is a fair comparison. (2) 
3.1.3 Explain why hydrogen bonds are stronger in compound B than in  compound A. (2) 
3.2 The vapour pressure values of a secondary and a tertiary alcohol are compared in the table below: 

3.2.1 Are compounds D and E STRUCTURAL isomers? Write down Yes or No. Give a reason for the answer. (3)
3.2.2 Which ONE of the two values, X or Y is HIGHER? Fully explain the answer. (4) [14]

QUESTION 4 
4.1 Study the two reactions shown below. P is an inorganic compound. R is an organic compound. 

1. : 3-methylbut-1-ene + P 1,2-dichloro-3-methylbutane 
2. : 2-bromobutane + Base R + NaBr + H2O

4.1.1 Write down the TYPE of reaction represented by: 

1.  Reaction I (1)
2. Reaction II (1)

4.1.2 Write down the: 

1.  STRUCTURAL formula of 1,2-dichloro-3-methylbutane (3) 
2. Name of the inorganic reactant P (1)

4.1.3 For reaction II write down: 

1. The structural formula and IUPAC name of the major  product, R (4) 
2. ONE reaction condition (1) 

4.2 The equation shown below shows n molecules of H₂C=CH₂ reacting to  produce a polymer. H₂C=CH₂ in the equation below represents small organic molecules  that can be covalently bonded to each other in a repeating pattern 

                         _{Polymerisation}
n H₂C=CH₂               →           [CH₂CH₂] 1000 

4.2.1 Is this reaction an example of ADDITION or CONDENSATION  polymerisation? (1) 
Write down: 
4.2.2 The value of n (1)
4.2.3 A term used for the underlined phrase (1)
4.2.4 ONE use of the polymer produced in this reaction (1) 
4.3 The following equation represents the cracking reaction of octane (C₈H₁₈).  Y is a straight chain organic compound. 

                  _{High temperature/High pressure}
 C₈H₁₈                             →                         Y + C₂H₄  

4.3.1 Define the term cracking reaction. (2) 
4.3.2 Is this reaction an example of THERMAL CRACKING or  CATALYTIC CRACKING? (1) 
4.3.3 Write down the STRUCTURAL FORMULA and IUPAC  name of compound Y. (4) [22] 

QUESTION 5 
Hydrogen peroxide (H₂O₂) decomposes according to the following equation:

2H₂O₂(aq) 2H₂O(ℓ) + O₂(g) 

5.1 State THREE factors that can INCREASE the rate of this reaction. (3)
5.2 Define the term reaction rate. (2) 
The rate of decomposition of hydrogen peroxide is investigated in THREE  experiments. The initial temperature of H₂O₂ is the same in ALL the  experiments. 
The reaction runs to completion in ALL the experiments. 
5.3 In experiment 1 a solution of hydrogen peroxide is heated to 35 °C. The concentration of H2O2 was measured at different time intervals during  the experiment. The following results were obtained: 

5.3.1 Calculate the average reaction rate, in mol·dm-3·min-1 during the  first 15 minutes. (3) 
5.3.2 Give a reason why the average reaction rate is HIGHER during the  first 15 minutes, compared to the time interval 100 to 215 seconds. (2) 
5.4 In experiment 2, a small amount of manganese dioxide is added to the same  H₂O₂ solution (used in experiment 1) and the mixture is heated to 35 °C. 

5.4.1 Is the reaction EXOTHERMIC or ENDOTHERMIC? (1) 
5.4.2 Use the collision theory to explain the effect of manganese dioxide  on the rate of decomposition of H₂O₂. (4) 
5.5 In experiment 3 the same volume of the solution of H₂O₂ (used in  experiment 1) is used but ONLY the temperature to which the solution is  heated is changed. The Maxwell-Boltzman distribution curves for experiment 1 and 3 are  shown below: 

5.5.1 Which experiment (1 or 3) was carried out at a HIGHER temperature? Give a reason for the answer. (2) 
5.5.2 How does the area under the graph of experiment 1 compare to the  area under the graph of experiment 3? Write down GREATER THAN, EQUAL TO or LESS THAN. Explain the answer. (2) 
5.6 In experiment 2 the total volume of oxygen produced at 35 °C is 0,2 dm³. Calculate the mass of H₂O₂ that decomposed in experiment 2 if the molar  volume of oxygen at 35 °C is 24,8 dm³·mol^-1. (5) 
5.7 The graphs below show how the concentration of H₂O₂ changes with time in  the experiments. 

Which graph (P, Q or R) represents the results of: 
5.7.1 Experiment 1 (1)
5.7.2 Experiment 2 (1) 
5.7.3 Experiment 3 (1) [27] 

QUESTION 6 
Carbon dioxide gas, CO₂(g), reacts with carbon, C(s), according to the following  balanced equation: 

CO₂(g) + C(s) ⇌ 2CO(g) 

The system reaches equilibrium at 1 000 °C. 
6.1 Define the term chemical equilibrium. (2) 
6.2 How will EACH of the following changes affect the number of moles of  CO(g) at equilibrium? Choose from INCREASES, DECREASES or REMAINS CONSTANT.
6.2.1 The addition of more carbon, C (1)
6.2.2 The addition of more CO₂ (1)
6.2.3 Decreasing the pressure by increasing the volume (1) 
6.3 Use Le Chatelier’s principle to explain the answer to QUESTION 6.2.3  above. (3) 
6.4 The sketch graph given below shows the changes in the rates of reaction  from the moment the reagents are introduced into the container. The  reaction reaches equilibrium for the first time at t₁. A change is made to the equilibrium mixture at t₂. 

6.4.1 Which reaction (FORWARD or REVERSE) is represented by the  broken line?  (1) 
6.4.2 What change was made at t₂? (2) 
Initially 104,72 g of CO₂ was heated with EXCESS carbon C in a sealed  flask of volume 250 cm³. The equilibrium mixture was found to contain  1,90 mol of CO₂. 
6.5 Calculate the value of the equilibrium constant, Kc at 1 000 °C. (8) 
6.6 The value of Kc for the reaction decreases to 0,333 when the temperature is  changed to 25 ^oC. 
6.6.1 Is there a HIGH or LOW yield at 25 ^oC? Give a reason for the answer. (2)
6.6.2 Is the FORWARD reaction ENDOTHERMIC or EXOTHERMIC? Explain the answer fully. (4) [25] 

QUESTION 7 
7.1 The hydrogen carbonate ion (HCO₃^-) undergoes hydrolysis according to the  equation: 

HCO₃^-(aq) + H₂O(ℓ) ⇌ CO₃^2-(aq) + H₃O⁺(aq)  

7.1.1 Define the term hydrolysis. (2)
7.1.2 Give a reason why HCO₃^-is regarded as an ampholyte. (2)
Write down the FORMULA of the: 
7.1.3 Conjugate acid of CO₃^2-(1)
7.1.4 Conjugate acid of HCO₃^-(not in the equation) (1) 
7.2 A weak monoprotic acid is dissolved in water to produce a solution of  accurately known concentration. 
7.2.1 Write down a term for the underlined phrase. (1) 
7.2.2 Which ONE of the following is an example of a weak monoprotic  acid? 

The weak monoprotic acid has a concentration of 0,2 mol.dm^-3. (2) 
7.2.3 Calculate the volume to which 20 cm³ of the acid must be diluted to  produce a solution with a concentration of 0,16 mol·dm^-3. (3)
7.3 During a titration a learner adds 30 cm³ of NaOH solution of concentration  0,1 mol.dm^-3 to an Erlenmeyer flask and titrates this solution with  25 cm³ HCℓ solution. The balanced equation for the reaction that takes  place is: 

NaOH + HCℓ NaCℓ + H₂O 

7.3.1 Name this type of reaction. (1) 
7.3.2 At what pH range will a suitable indicator for this titration change  colour? Choose from: 

Give a reason for the answer. (3) 
7.3.3 Calculate the concentration of the HCℓ that was used to neutralise  the NaOH in the Erlenmeyer flask. (4) 
The learner passes the endpoint by adding an extra 8 cm³ of the  HCℓ solution. 
7.3.4 Define the term endpoint. (2) 
7.3.5 Calculate the pH of the solution in the flask after the addition of  the extra 8 cm³ of HCℓ. (7) [29] 

TOTAL: 150

NATIONAL SENIOR CERTIFICATE 
DATA FOR PHYSICAL SCIENCES GRADE 12 
PAPER 2 (CHEMISTRY) 
TABLE 1: PHYSICAL CONSTANTS

TABLE 2: FORMULAE

TABLE 3: THE PERIODIC TABLE OF ELEMENTS