Physical Sciences Grade 12 Limpopo November 2016 QP

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE GRADE 12 PHYSICAL SCIENCES P2: CHEMISTRY SEPTEMBER 2016 MARKS: 150 TIME: 3 hours This question paper consists of 17 pages and 4 data sheets Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 2 Limpopo DoE/September 2016 NCS INSTRUCTIONS AND INFORMATION 1. Write your NAME in the appropriate space on the ANSWER BOOK. 2. This question paper consists of TEN questions. Answer ALL the questions in the ANSWER BOOK. 3. Start EACH question at the top of 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. Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 3 Limpopo DoE/September 2016 NCS QUESTION 1: MULTIPLE- CHOICE QUESTIONS Four options are provided as possible answers to the following questions. Each question has only ONE correct answer. Choose the answer and write only the letter (A – D) next to the question number (1.1 – 1.10) in the ANSWER BOOK, for example 1.11 E. 1.1 Which ONE of the following primary nutrients is mainly responsible for the production of healthy fruit in plants? A Potassium B Nitrogen C Phosphorous D Sulphur (2) 1.2 Which ONE of the following is a PRODUCT in ALL reactions of strong acids with strong bases? A Na+ B H3O+ C Cℓ- D H2O (2) 1.3 Which ONE of the following organic compounds is a FUNCTIONAL (group) isomer of butanoic acid? A 2-methylpropanoic acid B Methyl propanoate C Ethyl propanoate (2) D 2-methylpropan-2-ol 1.4 If a Table of Standard Reduction Potentials is compiled using θ magnesium as reference electrode, instead of using hydrogen(E red = 0, θ 00 V), what will the standard reduction potential, E red (V) of hydrogen be? A 0,00 V B - 2,36 V C +2,36 V D +1,18 V (2) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 4 Limpopo DoE/September 2016 NCS 1.5 If base P is titrated against acid Q, the pH of the solution at the end point is 9. Which ONE of the following combinations CORRECTLY represents base P and acid Q? BASE P ACID Q A KOH HNO3 B NaHCO3 HCℓ C NH3 H2SO4 D NaOH CH3COOH (2) 1.6 Three unknown gases, M, N and P are present in a mixture at equilibrium. At t1, a change is made to the equilibrium mixture as shown in the graph below. M Concentration N (mol∙dm-3) P  0 t1 Time(s) Which ONE of the following equations can represent the reaction that takes place? A 2M(g) ⇌ N(g) + P(g) B M(g) ⇌ N(g) + P(g) C M(g) + N(g) ⇌ P(g) (2) D M(g) + N(g) ⇌ 2P(g) 1.7 Which ONE of the following organic compounds has the LOWEST vapour pressure? A Ethanoic acid B Ethanal C Ethanol D Chloromethane (2) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 5 Limpopo DoE/September 2016 NCS 1.8 Consider the diagram below. Phase at room temperature GAS LIQUID Is it saturated? Is it saturated? Yes No Yes No W X Y Z Which ONE of the following letters can represent PROPANE? A W B X C Y D Z (2) 1.9 Which ONE of the following CORRECTLY describes the effect of a increase in temperature on a reaction at equilibrium? REACTION FAVOURED REACTION RATE A Exothermic Increases B Endothermic Decreases C Endothermic Increases D Exothermic Decreases (2) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 6 Limpopo DoE/September 2016 NCS 1.10 During a demonstration, a chemistry professor wants to electroplate a nickel coin with copper. Which ONE of the following actions will produce the desired result? A The electrolyte must contain nickel ions. B The nickel coin must be the cathode. C The cathode must be made of copper. D Electrons must flow from the nickel coin. (2) [20] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 7 Limpopo DoE/September 2016 NCS QUESTION 2 (Start on a New Page) The letters A to E in the table below represent six organic compounds. H H H3C A B C C C CH2 H H n H3C O C D CH3CH2CO2H CH3CH2CH2 CO CH3 CH3 Br E H3C CH CH2 CHCHCH2CH3 CH3 Use the information in the table to answer the questions that follow. 2.1 Write down the: 2.1.1 Homologous series to which compound C belongs (1) 2.1.2 Name of the functional group of compound D (1) 2.1.3 Letter that represents an UNSATURATED compound (1) 2.1.4 IUPAC name of compound E (3) 2.1.5 General formula of the homologous series to which compound A belongs (1) 2.1.6 STRUCTURAL FORMULA of the alcohol used in the preparation of compound C (2) 2.1.7 IUPAC name of compound D (1) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 8 Limpopo DoE/September 2016 NCS 2.2 The diagram below shows a bottle of mineral water. Label Bottle made of compound B Compound B is a polymer. Write down the: 2.2.1 NAME of compound B (1) 2.2.2 The type of polymerisation reaction that takes place during its formation (1) 2.2.3 Write down the empirical formula for: (a) Its monomer (1) (b) Compound B (1) [14] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 9 Limpopo DoE/September 2016 NCS QUESTION 3 (Start on a new page) The boiling points of compounds A, B and C from three different homologous series are determined under the same conditions. The table below shows the results obtained during the practical investigation. COMPOUND MOLECULAR MASS BOILING POINT(°C) (gmol-1) A CH3(CH2)2COOH 88,1 163 B CH3(CH2)3CH2OH 88,1 137 C CH3(CH2)3CHO 88,1 103 3.1 Define the term homologous series. (2) 3.2 Write down the homologous series to which the FUNCTIONAL (group) isomer of compound C belongs. (1) 3.3 Write down the IUPAC name of compound A. (1) 3.4 FROM THE TABLE ABOVE, write down: 3.4.1 The dependent variable for this investigation (1) 3.4.2 ONE controlled variable (1) 3.5 Refer to the table and state the conclusion that can be drawn from the results obtained. (1) 3.6 Refer to the TYPE and the STRENGTH of intermolecular forces to explain the difference in boiling points between compounds A and B. (3) 3.7 State the relationship between the strength of intermolecular forces and the vapour pressure of a substance. (1) [11] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 10 Limpopo DoE/September 2016 NCS QUESTION 4 (Start on a New Page) The flow diagram below shows how two organic compounds, X and Y, can be prepared with but-1-ene as the starting material. But-1-ene Reaction 1 HBr dilute KOH, heat Compound X Compound Y (major product) Reaction 2 (major product) 4.1 For reaction 1, write down the: 4.1.1 Type of reaction that takes place (1) 4.1.2 balanced equation using structural formulae (4) 4.1.3 IUPAC name of compound X (2) 4.2 For reaction 2, write down the: 4.2.1 Type of reaction that takes place (1) 4.2.2 STRUCTURAL FORMULA of compound Y (2) 4.2.3 IUPAC name of the positional isomer of compound Y (2) Concentrated sulphuric acid is added to compound Y and the mixture is heated. 4.3 Write down the STRUCTURAL FORMULA of the major organic product formed. (2) Reaction 2 is now repeated using concentrated KOH. 4.4 Write down the: 4.4.1 Homologous series to which the major product of this reaction belongs (1) 4.4.2 NAMES or FORMULAE of the INORGANIC products formed (2) [17] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 11 Limpopo DoE/September 2016 NCS QUESTION 5 (Start on a New Page) A group of grade 12 learners uses the reaction between calcium carbonate and hydrochloric acid to investigate one of the factors that influence reaction rate. They use the apparatus shown below. Gas X CaCO3 water HCℓ(aq) The reaction that takes place is represented by the following chemical equation: CaCO3(s) + 2HCℓ(aq)  CaCℓ2(aq) + X(g) + H2O(ℓ) ∆H < 0 5.1 Identify the gas X. (2) 5.2 Two experiments are conducted by using the apparatus shown above. The conditions for each experiment are given in the table below: Experiment Mass of State of Concentration Temperature CaCO3(s) division of HCℓ of HCℓ(aq) -3 (g) of (mol∙dm ) CaCO3(s) (°C) 1 4 lumps 0,2 40 2 4 lumps 0,4 40 5.2.1 Define, in words, the term reaction rate by referring to the concentration of hydrochloric acid. (2) 5.2.2 FROM THE TABLE ABOVE, write down the independent variable for this investigation. (1) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 12 Limpopo DoE/September 2016 NCS 5.2.3 Give a reason why the learners use equal masses and the same state of division of CaCO3(s). (1) The learners observe that the reaction rate is HIGHER in experiment 2 than in experiment 1. 5.2.4 Use the collision theory to explain this observation. (3) 5.2.5 Refer to experiment 2 and calculate the volume of hydrochloric acid (in cm3) that reacts with CaCO3(s). Assume that CaCO3 is the LIMITING REAGENT. (4) 5.3 Sketch a POTENTIAL ENERGY versus REACTION COORDINATE graph for this reaction. Label the axes and indicate the following on the graph: ∙ Heat of reaction ∙ Activation energy (4) ∙ Activated complex [17] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 13 Limpopo DoE/September 2016 NCS QUESTION 6 (Start on a New Page) A company uses the decomposition of phosphorus pentachloride, PCℓ5(g), at 200 °C to produce phosphorous trichloride, PCℓ3(g). The reaction which takes place in a sealed container is represented by the balanced equation below: PCℓ5(g) ⇋ PCℓ3(g) + Cℓ2(g) The results of the adjustments are shown in the graph below. Cℓ2(g) Concentration (mol·dm-3 ) PCℓ3(g ) PCℓ5(g ) 0 2 4 6 8 10 12 14 16 Time (min) 6.1 How much time was required for the system to come to chemical equilibrium for the FIRST time? (1) 6.2 How does the rate of the FORWARD reaction compare to that of the REVERSE reaction during the following time intervals: (Choose from GREATER THAN, EQUAL TO or LESS THAN) 6.2.1 0,0 – 2,0 minutes (1) 6.2.2 8,0 – 10,0 minutes (1) 6.3 Initially Phosphorus pentachloride, PCℓ5(g) of unknown mass x is injected into an empty 2 dm3 container at 200°C. At equilibrium, it is found that the concentration of PCℓ5(g) is 0,15 mol·dm-3. The Kc for this reaction at 200°C is 5,55. Calculate the initial mass of PCℓ5(g) gas injected into the container. (9) Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 14 Limpopo DoE/September 2016 NCS 6.4 If the change at t = 14 minutes is due to a decrease in temperature state whether the FORWARD reaction is ENDOTHERMIC or EXOTHERMIC. Use Le Chatelier’s principle to explain the answer. (3) [15] QUESTION 7 (Start on a New Page) 7.1 A laboratory technician prepares the following two dilute nitric acid solutions: 0,20 mol·dm-3 HNO3 solution ……………….(I) 0,30 mol·dm-3 HNO3 solution ……………….(II) 7.1.1 Distinguish between a concentrated acid and a dilute acid. (2) 7.1.2 Give a reason why nitric acid is classified as a strong acid. (2) 7.1.3 Determine the pH of solution (I) at 25 °C . (3) 7.2 A few crystals of sodium carbonate are added to water in a test tube. 7.2.1 Is the solution in the test tube ACIDIC, BASIC or NEUTRAL? (1) 7.2.2 Use a balanced ionic equation to explain the answer in QUESTION 7.2.1 (3) 7.3 A 25 g mass of impure sodium carbonate(Na2CO3) is treated with EXCESS dilute sulphuric acid. The balanced chemical equation for the reaction is: Na2CO3(aq) + H2SO4(aq)  Na2SO4 (aq)+ H2O (ℓ)+ CO2(g) During the reaction, 4.48 dm3 of carbon dioxide gas is collected at STP. Calculate the: 7.3.1 Percentage purity of the sodium carbonate (5) 7.3.2 Mass of the impurity (2) [18] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 15 Limpopo DoE/September 2016 NCS QUESTION 8 (Start on a New Page) A solid solution of silver and tin in mercury is used for filling tooth cavities. This solution is known as dental amalgam. Two of the reduction half-reactions that the filling can undergo are as follows: Eθ = +0,85 V 2+ 3 Hg2 (aq) + 4 Ag(s) + 6 e− → 2A g2 Hg3 (s) Sn (aq) + 3 Ag(s) + 2 e → Ag3 Sn(s) 2+ − Eθ = -0,05 V 8.1.1 Define the term reduction in terms of electron transfer. (2) 8.1.2 When a person whose tooth is filled with dental amalgam bites a piece of aluminium foil, the person experiences a sharp painful sensation, Refer to the relative strengths of reducing agents to explain the painful sensation in the tooth. (3) 8.2 Consider the following galvanic cell at 25 °C. Pt(s)|Cr2+ (1 mol·dm-3) , Cr3+ (1 mol·dm-3) || Cu2+ (1 mol·dm-3) | Cu(s) 8.2.1 Write down the balanced chemical equation for the net cell reaction that takes place. . (3) 8.2.2 Calculate the cell potential of this cell. (4) 8.2.3 How will the current produced by the cell be affected if the temperature of the electrolytes in the half cells is increased? Choose from INCREASES, DECREASES or REMAINS THE SAME. Use your knowledge of (3) REACTION RATE to give a reason for the answer. 8.2.4 Fully explain how the component represented by the double lines (||) functions to maintain electrical neutrality in the half cells. (2) [17] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 16 Limpopo DoE/September 2016 NCS QUESTION 9 (Start on a New Page) Aluminium metal is extracted from pure aluminium oxide (Aℓ2O3) in an electrolytic cell represented below. - + Electrode Y Aluminium oxide Molten aluminium Steel tank with brick lining 9.1 Write down the name of the ore from which aluminium is extracted. (2) 9.2 Name the element from which both electrode Y is made. (1) 9.3 State ONE reason why the anode of the cell must be replaced periodically (equation is NOT required). (1) 9.4 A “special impurity” is added to the purified aluminium oxide to lower the melting point to 950 °C. State the NAME of this “special impurity”. (1) 9.5 Write down the half-reaction that takes place at the cathode. (2) 9.6 In the reaction, 1890 C of charge produces 0,176 g of aluminium metal. Show by means of a calculation, that the charge on the cations of aluminium is +3. (Hint: 1 mol of electrons has a charge of 96 500 C) (3) [10] Copyright reserved Please turn over

Downloaded from hlayiso.com Physical Sciences /P2 17 Limpopo DoE/September 2016 NCS QUESTION 10 (Start on a New Page) 10.1 Fertilisers are increasingly used in agriculture and food production. 10.1.1 Suggest a reason for the increase in the use of fertilisers. (1) One of the properties of inorganic fertilisers is that they are soluble in water. 10.1.2 Why is this property important for the plant growth? (1) 10.1.3 State ONE disadvantage of the property mentioned in QUESTION 10.1.2 for farmers who use these fertilisers. (1) 10.2 The flow diagram below represents the 5 steps followed in the industrial preparation of fertiliser C Step 1 Step 2 Step 3 S SO2 SO3 Compound A O2 O2 98% H2SO4 Step 4 H2O Step 5 Fertiliser C Compound B NH3 10.2.1 State the NAME of the industrial process represented by steps 1-4 in the above flow diagram. (1) 10.2.2 State the chemical NAME of compound A. (1) 10.2.3 Write down a balanced equation for step 4. (3) 10.2.4 Write down the NAME or FORMULA of fertiliser C. (1) 10.2.5 For the primary nutrient in fertiliser C, write down: (a) Its function in plants (1) (b) The name of the process through which it is extracted (1) from the air [11] GRAND TOTAL: 150 ` Copyright reserved Please turn over

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