SENIOR CERTIFICATE EXAMINATION

Transcription

1 SENIOR ERTIFIATE EXAMINATION PYSIAL SIENES P2 EMISTRY 2015 MARKS: 150 TIME: 3 hours This question paper consists of 18 pages and 4 data sheets.

2 Physical Sciences/P2 2 DBE/2015 INSTRUTIONS AND INFORMATION Write your centre number and examination number in the appropriate spaces in the ANSWER BOOK. This question paper consists of TEN questions. Answer ALL the questions in the ANSWER BOOK. Start EA question on a NEW page in the ANSWER BOOK. Number the answers correctly according to the numbering system used in this question paper. Leave ONE line between two subquestions, for example between QUESTION 2.1 and QUESTION 2.2. You may use a non-programmable calculator. You may use appropriate mathematical instruments. You are advised to use the attached DATA SEETS. Show ALL formulae and substitutions in ALL calculations. Round off your final numerical answers to a minimum of TWO decimal places. Give brief motivations, discussions, et cetera where required. Write neatly and legibly.

3 Physical Sciences/P2 3 DBE/2015 QUESTION 1: MULTIPLE-OIE QUESTIONS Four options are provided as possible answers to the following questions. Each question has only ONE correct answer. hoose the answer and write only the letter (A D) next to the question number ( ) in the ANSWER BOOK, for example 1.11 E. 1.1 When a catalyst is used in a chemical reaction, it increases the A B D rate of the reaction. amount of products obtained. concentration of the products. concentration of the reactants. (2) 1.2 Which ONE of the following compounds is produced in the Ostwald process? A B D N 2 (g) N 3 (g) NO 3 (l) N 4 NO 3 (s) (2) 1.3 The addition of hydrogen to an alkene is known as... A B D hydration. cracking. hydrogenation. hydrohalogenation. (2) 1.4 Which ONE of the following compounds has the highest boiling point? A B D (2)

4 Physical Sciences/P2 4 DBE/ onsider the reaction represented by the balanced equation below: 2SO 3 (g) 2SO 2 (g) + O 2 (g) = 198 kj mol -1 Which ONE of the following is TRUE for this reaction? When 2 moles of SO 2 (g) are formed... A B D 198 kj of energy are absorbed. 198 kj of energy are released. 396 kj of energy are absorbed. 396 kj of energy are released. (2) 1.6 Which ONE of the following compounds belongs to the same homologous series as but-2-yne? A B D (2) 1.7 The equilibrium constant, K c, for the reaction A(g) B(g) is 1 x Which ONE of the following statements is always ORRET for this reaction? The mixture at equilibrium consists of... A B D equal amounts of A(g) and B(g). very little of A(g). mostly A(g). mostly B(g). (2)

5 Physical Sciences/P2 5 DBE/ The simplified diagram below shows a cell that can be used to purify copper. Electrode X Electrode Y opper(ii) solution The purification failed. Which ONE of the following is the most likely reason for the failure? A B D A D source is used. Electrode X is the anode. Electrode Y is the impure copper. Electrode Y is a carbon rod. (2) 1.9 A galvanic cell consists of the following half-cells: Pt(s) l 2 (g) l - (aq) AND u 2+ (aq) u(s) Which ONE of the following statements is TRUE while the cell is functioning? A B D u(s) is oxidised. l - (aq) is reduced. l 2 (g) acts as reducing agent. u(s) acts as oxidising agent. (2)

6 Physical Sciences/P2 6 DBE/ Which ONE of the following weak acids, each of concentration 0,1 mol dm -3, has the lowest 3 O + (aq) concentration? AID K a VALUE A 2 SO 3 (aq) 1,2 x 10-2 B 2 O 3 (aq) 4,2 x 10-7 (OO) 2 (aq) 5,6 x 10-2 D 2 S(aq) 1,0 x 10-7 (2) [20]

7 Physical Sciences/P2 7 DBE/2015 QUESTION 2 (Start on a new page.) The letters A to F in the table below represent six organic compounds. O A O B l 4 8 D 3 2 O 3 E 3 ( 3 ) 2 O F Use the information in the table (where applicable) to answer the questions that follow. 2.1 Write down the LETTER that represents a compound that: (A compound may be used more than once.) Is a haloalkane (1) as a hydroxyl group as functional group (1) Belongs to the same homologous series as ethanoic acid (1) 2.2 Write down the: IUPA name of compound B (3) IUPA name of compound E (2) Structural formula of the functional group of compound D (1)

8 Physical Sciences/P2 8 DBE/ ompound has AIN and POSITIONAL isomers Define the term positional isomer. (2) Write down the IUPA name of each of the TWO positional isomers of compound. (4) Write down the structural formula of a chain isomer of compound. (2) 2.4 ompound F reacts at high pressure and high temperature to form compounds P and Q as given below. P + ompound F ompound Q Write down the: Type of reaction that takes place (1) IUPA name of compound Q (1) Molecular formula of compound P (1) ompound Q is the monomer of a polymer used to make plastic bags Write down the NAME and ONDENSED FORMULA of this polymer. (3) [23]

9 Physical Sciences/P2 9 DBE/2015 QUESTION 3 (Start on a new page.) onsider the incomplete equations of two reactions below. X represents the organic product formed in reaction 1, which is a SUBSTITUTION REATION. In reaction 2, X reacts with reactant Y as shown. Reaction 1: 2 5 Br strong base NaBr + X Reaction 2: X + Y oncentrated 2 SO O O 3.1 onsider reaction 1. Write down the: Type of substitution reaction that takes place (1) TWO reaction conditions (2) IUPA name of compound X (1) 3.2 onsider reaction 2. Write down the: Type of reaction that takes place (1) Structural formula of compound Y (2) IUPA name of the organic product (2) [9]

10 Physical Sciences/P2 10 DBE/2015 QUESTION 4 (Start on a new page.) The table below shows five organic compounds represented by the letters A to E. A 4 B D E 3 2 O 4.1 Is compound B SATURATED or UNSATURATED? Give a reason for the answer. (2) onsider the boiling points of compounds A to E given in random order below and use them, where applicable, to answer the questions that follow Write down the boiling point of: ompound (1) ompound E (1) 4.3 Explain the difference in boiling points of compounds and E by referring to the TYPE of intermolecular forces present in EA of these compounds. (3) 4.4 Does vapour pressure INREASE or DEREASE from compounds A to D? Fully explain the answer. (4) 4.5 ow will the vapour pressure of 2-methylpropane compare to the vapour pressure of compound D? Write down only IGER TAN, LOWER TAN or EQUAL TO. (1) [12]

11 Physical Sciences/P2 11 DBE/2015 QUESTION 5 (Start on a new page.) A group of learners uses the reaction of clean magnesium ribbon with dilute hydrochloric acid to investigate factors that influence reaction rate. The balanced equation for the reaction is: Mg(s) + 2l(aq) Mgl 2 (aq) + 2 (g) < Is the above reaction EXOTERMI or ENDOTERMI? Give a reason for the answer. (2) 5.2 In one of the experiments 5 g magnesium ribbon was added to the hydrochloric acid solution If 30 cm 3 dilute hydrochloric acid solution of concentration 1,5 mol dm -3 is USED UP in 1 minute, calculate the average reaction rate in mol s -1. (5) The volume of hydrogen gas produced as a function of time in this experiment is represented by graph S below. (The graph is NOT drawn to scale.) Volume (cm 3 ) S 0 t 1 t 2 t 3 Time (s) ow does the rate of the reaction change between: (Write down INREASES, DEREASES or NO ANGE.) (a) t 1 and t 2 Use the collision theory to explain the answer. (4) (b) t 2 and t 3 Give a reason for the answer without referring to the graph. (2)

12 Physical Sciences/P2 12 DBE/ In another experiment they add 5 g of magnesium to 30 cm 3 of dilute hydrochloric acid of concentration 1,5 mol dm -3. They obtained graph T below. (The graph is NOT drawn to scale.) Volume (cm 3 ) T S Time (s) Give TWO possible reasons why graph T differs from graph S. (2) [15]

13 Physical Sciences/P2 13 DBE/2015 QUESTION 6 (Start on a new page.) Initially excess N 4 S(s) is placed in a 5 dm 3 container at 218. The container is sealed and the reaction is allowed to reach equilibrium according to the following balanced equation: N 4 S(s) N 3 (g) + 2 S(g) > State Le hatelier's principle. (2) 6.2 What effect will each of the following changes have on the amount of N 3 (g) at equilibrium? Write down only INREASES, DEREASES or REMAINS TE SAME More N 4 S(s) is added (1) The temperature is increased (1) 6.3 The equilibrium constant for this reaction at 218 is 1,2 x alculate the minimum mass of N 4 S(s) that must be sealed in the container to obtain equilibrium. (6) The pressure in the container is now increased by decreasing the volume of the container at constant temperature. 6.4 ow will this change affect the number of moles of 2 S(g) produced? Fully explain the answer. (3) [13]

14 Physical Sciences/P2 14 DBE/2015 QUESTION 7 (Start on a new page.) Anhydrous oxalic acid is an example of an acid that can donate two protons and thus ionises in two steps as represented by the equations below: I: (OO) 2 (aq) + 2 O(l) 3 O + (aq) + (OO) 2 (aq) II: (OO) (aq) + 2 2O(l) 3 O + (aq) + (OO) 2 (aq) Write down: ONE word for the underlined phrase in the above sentence (1) The FORMULA of each of the TWO bases in reaction II (2) The FORMULA of the substance that acts as ampholyte in reactions I and II. Give a reason for the answer. (2) 7.2 Give a reason why oxalic acid is a weak acid. (1) 7.3 A standard solution of (OO) 2 of concentration 0,20 mol dm -3 is prepared by dissolving a certain amount of (OO) 2 in water in a 250 cm 3 volumetric flask. alculate the mass of (OO) 2 needed to prepare the standard solution. (4)

15 Physical Sciences/P2 15 DBE/ During a titration 25 cm 3 of the standard solution of (OO) 2 prepared in QUESTION 7.3 is neutralised by a sodium hydroxide solution from a burette. The balanced equation for the reaction is: (OO) 2 (aq) + 2NaO(aq) (OONa) 2 (aq) O(l) The diagrams below show the burette readings before the titration commenced and at the endpoint respectively. Before the titration cm 3 At the endpoint cm Level of NaO(aq) 39 Level of NaO(aq) Use the burette readings and calculate the concentration of the sodium hydroxide solution. (5) Write down a balanced equation that explains why the solution has a p greater than 7 at the endpoint. (3) [18]

16 Physical Sciences/P2 16 DBE/2015 QUESTION 8 (Start on a new page.) Learners set up an electrochemical cell, shown in the simplified diagram below, using magnesium and lead as electrodes. Nitrate solutions are used as electrolytes in both half-cells. V Electrode P String dipped in KNO 3 (aq) + Electrode Q Electrolyte Electrolyte alf-cell A alf-cell B 8.1 What type of reaction (NEUTRALISATION, REDOX or PREIPITATION) takes place in this cell? (1) 8.2 Which electrode, P or Q, is magnesium? Give a reason for the answer. (2) 8.3 Write down the: Standard conditions under which this cell functions (2) ell notation for this cell (3) NAME or FORMULA of the oxidising agent in the cell (1) 8.4 alculate the initial emf of the cell above under standard conditions. (4) 8.5 ow will the voltmeter reading change if the: (Write down only INREASES, DEREASES or REMAINS TE SAME.) Size of electrode P is increased (1) Initial concentration of the electrolyte in half-cell B is increased (1) [15]

17 Physical Sciences/P2 17 DBE/2015 QUESTION 9 (Start on a new page.) The diagram below shows a simplified electrolytic cell that can be used to electroplate a plastic ring with nickel. Prior to electroplating the ring is covered with a graphite layer. Battery Plastic ring coated with graphite NiSO 4 (aq) Nickel electrode 9.1 Define the term electrolyte. (2) 9.2 Give ONE reason why the plastic ring must be coated with graphite prior to electroplating. (1) 9.3 Write down the: alf-reaction that occurs at the plastic ring (2) NAME or FORMULA of the reducing agent in the cell. Give a reason for the answer. (2) 9.4 Which electrode, the RING or NIKEL, is the cathode? Give a reason for the answer. (2) The nickel electrode is now replaced with a carbon rod. 9.5 ow will the concentration of the electrolyte change during electroplating? Write down only INREASES, DEREASES or NO ANGE. Give a reason for the answer. (2) [11]

18 Physical Sciences/P2 18 DBE/2015 QUESTION 10 (Start on a new page.) The industrial process for the preparation of sulphuric acid involves a series of stages. The second stage in this process involves the conversion of sulphur dioxide into sulphur trioxide in a converter as illustrated below. In the converter the gases are passed over vanadium pentoxide (V 2 O 5 ) placed in layers as shown below. Sulphur dioxide and air onverter V 2 O 5 V 2 O 5 V 2 O 5 V 2 O 5 layer 1 layer 2 layer 3 layer 4 Gas outlet 10.1 Write down the: Balanced equation for the reaction taking place in the converter (3) Function of the vanadium pentoxide (1) The table below shows data obtained during the second stage. VANADIUM PENTOXIDE LAYER TEMPERATURE OF GAS BEFORE TE REATION ( ) TEMPERATURE OF GAS AFTER TE REATION ( ) PERENTAGE OF REATANT ONVERTED TO PRODUT , Is the reaction in the second stage EXOTERMI or ENDOTERMI? Refer to the data in the table to give a reason for the answer. (2) 10.3 After the conversion at each layer the gases are cooled down to 450. Fully explain why the gases must be cooled to this temperature. (3) 10.4 During the third stage sulphur trioxide is dissolved in sulphuric acid rather than in water to produce oleum Write down the FORMULA of oleum. (1) Give a reason why sulphur trioxide is not dissolved in water. (1) 10.5 Sulphuric acid reacts with ammonia to form a fertiliser. Write down a balanced equation for this reaction. (3) [14] TOTAL: 150

19 Physical Sciences/P2 1 DBE/2015 DATA FOR PYSIAL SIENES GRADE 12 PAPER 2 (EMISTRY) GEGEWENS VIR FISIESE WETENSKAPPE GRAAD 12 VRAESTEL 2 (EMIE) TABLE 1: PYSIAL ONSTANTS/TABEL 1: FISIESE KONSTANTES NAME/NAAM SYMBOL/SIMBOOL VALUE/WAARDE Standard pressure Standaarddruk θ p 1,013 x 10 5 Pa Molar gas volume at STP Molêre gasvolume by STD V m 22,4 dm 3 mol -1 Standard temperature Standaardtemperatuur θ T 273 K harge on electron Lading op elektron e -1,6 x Avogadro's constant Avogadro-konstante N A 6,02 x mol -1 TABLE 2: FORMULAE/TABEL 2: FORMULES m n= M n c = or/of V cava na c v n b b b c = m MV n= n= N N A V V m = p = -log[ 3 O + ] K w = [ 3 O + ][O - ] = 1 x at/by 298 K E θ cell θ θ θ = E E / E = E E θ cathode θ anode sel katode anode or/of θ θ θ θ θ θ E = E E / E = E E cell reduction oxidation sel reduksie oksidasie or/of θ θ θ θ θ θ E = E E / E = E E cell oxidising agent reducing agent sel oksideermiddel reduseermiddel

20 Physical Sciences/P2 2 DBE/2015 TABLE 3: TE PERIODI TABLE OF ELEMENTS 1 (I) 2 (II) (III) 14 (IV) 15 (V) 16 (VI) 17 (VII) 18 (VIII) 2, e 4 1,0 3 Li 7 1,5 4 Be 9 2,0 5 B 11 2, ,0 7 N 14 3,5 8 O 16 4,0 9 F Ne 20 0,9 11 Na 23 1,2 12 Mg 24 1,5 13 Al 27 1,8 14 Si 28 2,1 15 P 31 2,5 16 S 32 3,0 17 l 35,5 18 Ar 40 0,8 19 K 39 1,0 20 a 40 1,3 21 Sc 45 1,5 22 Ti 48 1,6 23 V 51 1,6 24 r 52 1,5 25 Mn 55 1,8 26 Fe 56 1,8 27 o 59 1,8 28 Ni 59 1,9 29 u 63,5 1,6 30 Zn 65 1,6 31 Ga 70 1,8 32 Ge 73 2,0 33 As 75 2,4 34 Se 79 2,8 35 Br Kr 84 0,8 37 Rb 86 1,0 38 Sr 88 1,2 39 Y 89 1,4 40 Zr Nb 92 1,8 42 Mo 96 1,9 43 Tc 2,2 44 Ru 101 2,2 45 Rh 103 2,2 46 Pd 106 1,9 47 Ag 108 1,7 48 d 112 1,7 49 In 115 1,8 50 Sn 119 1,9 51 Sb 122 2,1 52 Te 128 2,5 53 I Xe 131 0,7 55 s 133 0,9 56 Ba La 139 1,6 72 f Ta W Re Os Ir Pt Au g 201 1,8 81 Tl 204 1,8 82 Pb 207 1,9 83 Bi 209 2,0 84 Po 2,5 85 At 86 Rn 0,7 87 Fr 0,9 88 Ra Ac 58 e Pr Nd Pm 62 Sm Eu Gd Tb Dy o Er Tm Yb Lu Th Pa 92 U Np 94 Pu 95 Am 96 m 97 Bk 98 f 99 Es 100 Fm 101 Md 102 No 103 Lr Electronegativity Elektronegatiwiteit Approximate relative atomic mass Benaderde relatiewe atoommassa Atomic number Atoomgetal 29 u 63,5 1,9 Symbol Simbool KEY/SLEUTEL

21 Physical Sciences/P2 3 DBE/2015 TABLE 4A: STANDARD REDUTION POTENTIALS TABEL 4A: STANDAARD-REDUKSIEPOTENSIALE Increasing oxidising ability/toenemende oksiderende vermoë alf-reactions/alfreaksies θe (V) F 2(g) + 2e 2F + 2,87 o 3+ + e o ,81 2O e 2 2O +1,77 MnO e Mn O + 1,51 l 2(g) + 2e 2l + 1,36 r 2O e 2r O + 1,33 O 2(g) e 2 2O + 1,23 MnO e Mn O + 1,23 Pt e Pt + 1,20 Br 2(l) + 2e 2Br + 1,07 NO e NO(g) + 2 2O + 0,96 g e g(l) + 0,85 Ag + + e Ag + 0,80 NO e NO 2(g) + 2O + 0,80 Fe 3+ + e Fe ,77 O 2(g) e 2O 2 + 0,68 I 2 + 2e 2I + 0,54 u + + e u + 0,52 SO e S + 2 2O + 0,45 2 2O + O 2 + 4e 4O + 0,40 u e u + 0,34 SO e SO 2(g) + 2 2O + 0,17 u 2+ + e u + + 0,16 Sn e Sn ,15 S e 2S(g) + 0, e 2(g) 0,00 Fe e Fe 0,06 Pb e Pb 0,13 Sn e Sn 0,14 Ni e Ni 0,27 o e o 0,28 d e d 0,40 r 3+ + e r 2+ 0,41 Fe e Fe 0,44 r e r 0,74 Zn e Zn 0,76 2 2O + 2e 2(g) + 2O 0,83 r e r 0,91 Mn e Mn 1,18 Al e Al 1,66 Mg e Mg 2,36 Na + + e Na 2,71 a e a 2,87 Sr e Sr 2,89 Ba e Ba 2,90 s + + e - s - 2,92 K + + e K 2,93 Li + + e Li 3,05 Increasing reducing ability/toenemende reduserende vermoë

22 θe Physical Sciences/P2 4 DBE/2015 TABLE 4B: STANDARD REDUTION POTENTIALS TABEL 4B: STANDAARD-REDUKSIEPOTENSIALE alf-reactions/alfreaksies (V) Li + + e Li 3,05 K + + e K 2,93 s + + e s 2,92 Ba e Ba 2,90 Sr e Sr 2,89 a e a 2,87 Na + + e Na 2,71 Mg e Mg 2,36 Al e Al 1,66 Mn e Mn 1,18 r e r 0,91 2 2O + 2e 2(g) + 2O 0,83 Zn e Zn 0,76 r e r 0,74 Fe e Fe 0,44 r 3+ + e r 2+ 0,41 d e d 0,40 o e o 0,28 Ni e Ni 0,27 Sn e Sn 0,14 Pb e Pb 0,13 Fe e Fe 0, e 2(g) 0,00 S e 2S(g) + 0,14 Sn e Sn ,15 u 2+ + e u + + 0,16 SO e SO 2(g) + 2 2O + 0,17 Increasing oxidising ability/toenemende oksiderende vermoë u e u + 0,34 2 2O + O 2 + 4e 4O + 0,40 SO e S + 2 2O + 0,45 u + + e u + 0,52 I 2 + 2e 2I + 0,54 O 2(g) e 2O 2 + 0,68 Fe 3+ + e Fe ,77 NO e NO 2(g) + 2O + 0,80 Ag + + e Ag + 0,80 g e g(l) + 0,85 NO e NO(g) + 2 2O + 0,96 Br 2(l) + 2e 2Br + 1,07 Pt e Pt + 1,20 MnO e Mn O + 1,23 O 2(g) e 2 2O + 1,23 r 2O e 2r O + 1,33 l 2(g) + 2e 2l + 1,36 MnO e Mn O + 1,51 2O e 2 2O +1,77 o 3+ + e o ,81 F 2(g) + 2e 2F + 2,87 Increasing reducing ability/toenemende reduserende vermoë