NATIONAL SENIOR CERTIFICATE GRADE 12

Transcription

1 NTIONL SENIOR ERTIFITE GRDE 12 PYSIL SIENES: EMISTRY (P2) FERURY/MR 2016 MRKS: 150 TIME: 3 hours This question paper consists of 15 pages, 4 data sheets and 1 graph sheet. opyright reserved

2 Physical Sciences/P2 2 DE/Feb. Mar NS INSTRUTIONS ND INFORMTION Write your centre number and examination number in the appropriate spaces in the NSWER OOK and on the GRP SEET. This question paper consists of TEN questions. nswer QUESTION on the attached GRP SEET. nswer LL the questions in the NSWER OOK. Start E question on a NEW page in the NSWER OOK. 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 DT SEETS. Show LL formulae and substitutions in LL 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. opyright reserved

3 Physical Sciences/P2 3 DE/Feb. Mar NS 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 ( D) next to the question number ( ) in the NSWER OOK, for example 1.11 E. 1.1 Which ONE of the following compounds is an aldehyde? D 3 O O 3 2 OO O (2) 1.2 The equation below represents the decomposition of calcium carbonate. ao 3 (s) ao(s) + O 2 (g) Which ONE of the following factors will increase the initial rate of decomposition of calcium carbonate? D Pressure Temperature oncentration Mass of ao 3 (s) (2) 1.3 onsider the cell notation of the galvanic cell below. Zn Zn 2+ u 2+ u Which ONE of the following statements regarding this cell is TRUE? D opper is formed at the cathode. opper is formed at the anode. Zinc is formed at the anode. Zinc is formed at the cathode. (2) opyright reserved

4 Physical Sciences/P2 4 DE/Feb. Mar NS 1.4 Which ONE of the following compounds will react with sodium hydroxide (NaO) in a neutralisation reaction? D 3 O 3 OO 3 O O (2) 1.5 onsider the reactant Y in the following reaction: The formula of Y is: Y + 2 O 3 O PO 4 D 3 PO 4 2PO 4 2 PO 4 3 PO 4 (2) 1.6 gardener needs a fertiliser with the highest percentage of the relevant nutrient to obtain a green lawn. Which ONE of the following NPK fertilisers will give the best results? D 8 : 1 : 5 7 : 1 : 1 3 : 2 : 3 3 : 1 : 5 (2) opyright reserved

5 Physical Sciences/P2 5 DE/Feb. Mar NS 1.7 The activation energy for a certain reaction is 50 kj mol -1. Energy is absorbed when this reaction takes place. Which ONE of the following is ORRET for the REVERSE reaction? TIVTION ENERGY (E ) ET OF RETION (Δ) E > 50 kj mol -1 Δ > 0 E > 50 kj mol -1 Δ < 0 E < 50 kj mol -1 Δ < 0 D E < 50 kj mol -1 Δ > 0 (2) 1.8 Which ONE of the following pairs of compounds are FUNTIONL isomers? D Methanol and methanal utane and 2-methylpropane Propan-1-ol and propan-2-ol Propanoic acid and methyl ethanoate (2) 1.9 The balanced equations for three reactions at equilibrium in a closed container are given below. (i) 2 4 (g) + 2 (g) 2 6 (g) (ii) Fe 3 O 4 (s) (g) 3Fe(s) O(g) (iii) SO 3 (g) + NO(g) NO 2 (g) + SO 2 (g) In which reaction(s) will the equilibrium position shift when the volume of the reaction vessel is decreased at constant temperature? D (i) only (i) and (ii) only (i) and (iii) only (i), (ii) and (iii) (2) opyright reserved

6 Physical Sciences/P2 6 DE/Feb. Mar NS 1.10 In each of the electrolytic cells below, copper(ii) sulphate is used as the electrolyte. The electrodes are either carbon () or copper (u). (i) (ii) (iii) u u u u In which cell(s) will the concentration of the electrolyte remain constant during electrolysis? D (i) only (i) and (ii) only (i) and (iii) only (ii) and (iii) only (2) [20] opyright reserved

7 Physical Sciences/P2 7 DE/Feb. Mar NS QUESTION 2 (Start on a new page.) 2.1 onsider the organic compounds represented by the letters to below. l l O O Write down the: Name of the homologous series to which compound belongs (1) IUP name of compound (3) Structural formula of a tertiary alcohol that is a structural isomer of compound (2) 2.2 n alcohol and methanoic acid are heated in the presence of concentrated sulphuric acid to form an ester What is the role of the concentrated sulphuric acid in this reaction? (1) Write down the NME or FORMUL of the inorganic product formed. (1) The ester contains 6,67% hydrogen (), 40% carbon () and 53,33% oxygen (O). The molar mass of the ester is 60 g mol -1. Use a calculation to determine its: Empirical formula (5) Molecular formula (3) Write down the: Structural formula of methanoic acid (1) IUP name of the ester (2) [19] opyright reserved

8 Physical Sciences/P2 8 DE/Feb. Mar NS QUESTION 3 (Start on a new page.) 3.1 Define the term boiling point. (2) 3.2 What is the relationship between strength of intermolecular forces and boiling point? (1) The relationship between strength of intermolecular forces and boiling point is investigated using four organic compounds from different homologous series. The compounds and their boiling points are given in the table below. OMPOUND OILING POINT ( ) Propane -42 Propan-2-one 56 Propan-1-ol 97 D Propanoic acid Refer to the TYPE and the STRENGT of intermolecular forces to explain the difference in boiling points between: ompounds and (3) ompounds and D (3) 3.4 Is compound a GS or a LIQUID at room temperature? (1) [10] opyright reserved

9 Physical Sciences/P2 9 DE/Feb. Mar NS QUESTION 4 (Start on a new page.) The flow diagram below shows different organic reactions using 2 = 2 as the starting reactant. X, Y and Z represent different organic compounds. 2 6 Reaction 4 2 = 2 Reaction 1 Y Reaction 2 + l X Reaction 3 Z 4.1 During Reaction 1, 2 = 2 undergoes polymerisation to form compound Y. For this reaction, write down the: Type of polymerisation (1) NME of compound Y (1) 4.2 For Reaction 2, write down the: IUP name of compound X (2) Type of addition reaction of which this is an example (1) 4.3 During Reaction 3, compound X reacts with excess hot water. Write down the: STRUTURL FORMUL of compound Z (2) NME or FORMUL of the INORGNI product (1) 4.4 Reaction 4 is an addition reaction Is 2 6 a STURTED or an UNSTURTED compound? Give a reason for the answer. (2) Write down the NME or FORMUL of the INORGNI reactant needed for this reaction. (1) Using molecular formulae, write down a balanced equation for the complete combustion of 2 6. (3) [14] opyright reserved

10 Physical Sciences/P2 10 DE/Feb. Mar NS QUESTION 5 (Start on a new page.) NOTE: The graph for QUESTION must be drawn on the GRP SEET attached at the end of the QUESTION PPER. Methanol and hydrochloric acid react according to the following balanced equation: 3 O(aq) + l(aq) 3 l(aq) + 2 O(l) 5.1 State TWO factors that can INRESE the rate of this reaction. (2) 5.2 Define the term reaction rate. (2) 5.3 The rate of the reaction between methanol and hydrochloric acid is investigated. The concentration of l(aq) was measured at different time intervals. The following results were obtained: TIME (MINUTES) l ONENTRTION (mol dm -3 ) 0 1, , , , , alculate the average reaction rate, in (mol dm -3 ) min -1 during the first 15 minutes. (3) Use the data in the table to draw a graph of concentration versus time on the attached GRP SEET. NOTE: The graph is not a straight line. (TT TIS GRP SEET TO YOUR NSWER OOK.) (3) From the graph, determine the concentration of l(aq) at the 40 th minute. (1) Use the collision theory to explain why the reaction rate decreases with time. ssume that the temperature remains constant. (3) alculate the mass of 3 l(aq) in the flask at the 215 th minute. The volume of the reagents remains 60 cm 3 during the reaction. (5) [19] opyright reserved

11 Physical Sciences/P2 11 DE/Feb. Mar NS QUESTION 6 (Start on a new page.) Initially, 2,2 g of pure O 2 (g) is sealed in an empty 5 dm 3 container at alculate the initial concentration of O 2 (g). (4) 6.2 Give a reason why equilibrium will not be established. (1) ao 3 (s) is now added to the 2,2 g O 2 (g) in the container and after a while equilibrium is established at 900 according to the following balanced equation: ao 3 (s) ao(s) + O 2 (g) The equilibrium constant for this reaction at 900 is 0, Give a reason why this reaction will only reach equilibrium in a SELED container. (1) 6.4 alculate the minimum mass of ao 3 (s) that must be added to the container to achieve equilibrium. (7) 6.5 ow will E of the following changes affect the amount of O 2 (g)? Write down only INRESES, DERESES or REMINS TE SME More ao 3 (s) is added at 900 (1) The pressure is increased (1) 6.6 It is found that the equilibrium constant (K c ) for this reaction is 2,6 x 10-6 at 727. Is the reaction EXOTERMI or ENDOTERMI? Fully explain how you arrived at the answer. (4) [19] opyright reserved

12 Physical Sciences/P2 12 DE/Feb. Mar NS QUESTION 7 (Start on a new page.) 7.1 Define an acid in terms of the Lowry-rønsted theory. (2) 7.2 arbonated water is an aqueous solution of carbonic acid, 2 O 3. 2 O 3 (aq) ionises in two steps when it dissolves in water Write down the FORMUL of the conjugate base of 2 O 3 (aq). (1) Write down a balanced equation for the first step in the ionisation of carbonic acid. (3) The p of a carbonic acid solution at 25 is 3,4. alculate the hydroxide ion concentration in the solution. (5) 7.3 X is a monoprotic acid State the meaning of the term monoprotic. (1) sample of acid X is titrated with a standard sodium hydroxide solution using a suitable indicator. t the endpoint it is found that 25 cm 3 of acid X is neutralised by 27,5 cm 3 of the sodium hydroxide solution of concentration 0,1 mol dm -3. alculate the concentration of acid X. (5) The concentration of 3 O + ions in the sample of acid X is 2,4 x 10-4 mol dm -3. Is acid X a WEK or a STRONG acid? Explain the answer by referring to the answer in QUESTION (3) [20] opyright reserved

13 Physical Sciences/P2 13 DE/Feb. Mar NS QUESTION 8 (Start on a new page.) n electrochemical cell consisting of half-cells and is assembled under standard conditions as shown below. alf-cell Pt, l 2 (101,3 kpa) l - (1 mol dm -3 ) alf-cell Mg 2+ (1 mol dm -3 ) Mg(s) 8.1 t which half-cell, or, are electrons released into the external circuit? (1) 8.2 Write down the: Reduction half-reaction that takes place in this cell (2) NME or FORMUL of the substance whose oxidation number DERESES (1) 8.3 alculate the initial cell potential of this cell when it is in operation. (4) 8.4 Write down an observation that will be made in half-cell as the cell operates. Give a reason for the answer. (2) [10] opyright reserved

14 Physical Sciences/P2 14 DE/Feb. Mar NS QUESTION 9 (Start on a new page.) The electrochemical cell below is set up to demonstrate the purification of copper. opper(ii) chloride solution 9.1 Write down the type of electrochemical cell illustrated above. (1) The graphs below show the change in mass of the electrodes whilst the cell is in operation. Mass (g) P Q Time (min.) 9.2 Define a reducing agent in terms of electron transfer. (2) 9.3 Which graph represents the change in mass of electrode? (1) 9.4 Write down the half-reaction that takes place at electrode. (2) 9.5 Electrodes and are now replaced by graphite electrodes. It is observed that chlorine gas (l 2 ) is released at one of the electrodes. t which electrode ( or ) is chlorine gas formed? Fully explain how it is formed. (3) [9] opyright reserved

15 Physical Sciences/P2 15 DE/Feb. Mar NS QUESTION 10 (Start on a new page.) mmonium nitrate is an important fertiliser. It is produced by reacting nitric acid with ammonia. oth nitric acid and ammonia are prepared on a large scale in industry Write down the name of the industrial preparation of nitric acid. (1) 10.2 The catalytic oxidation of ammonia is one of the steps in the process named in QUESTION Write down the NMES or FORMULE of the TWO products formed in this step. (2) 10.3 Write down a balanced equation for the preparation of ammonium nitrate. (3) 10.4 alculate the mass, in kilogram, of ammonium nitrate that can be made from 6,8 x 10 4 kg of ammonia and excess nitric acid. (One mole of ammonia produces one mole of ammonium nitrate.) (3) 10.5 mmonium nitrate is often mixed with potassium chloride and ammonium phosphate. Give a reason why it is mixed with these compounds. (1) [10] TOTL: 150 opyright reserved

16 Physical Sciences/P2 DE/Feb. Mar NS DT FOR PYSIL SIENES GRDE 12 PPER 2 (EMISTRY) GEGEWENS VIR FISIESE WETENSKPPE GRD 12 VRESTEL 2 (EMIE) TLE 1: PYSIL ONSTNTS/TEL 1: FISIESE KONSTNTES NME/NM SYMOL/SIMOOL VLUE/WRDE Standard pressure Standaarddruk 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 T 273 K harge on electron Lading op elektron e -1,6 x vogadro's constant vogadro-konstante N 6,02 x mol -1 TLE 2: FORMULE/TEL 2: FORMULES m n= M n c = or/of V cava na c v n b b b m c = MV n= n= N N V V m = p = -log[ 3 O + ] K w = [ 3 O + ][O - ] = 1 x at/by 298 K E cell = E E / E cathode anode sel = E katode E anode or/of E = E E / E cell reduction oxidation sel = E reduksie E oksidasie or/of E = E E / E cell oxidising agent reducing agent sel = E oksideermiddel E reduseermiddel opyright reserved

17 Physical Sciences/P2 DE/Feb. Mar NS opyright reserved TLE 3: TE PERIODI TLE OF ELEMENTS TEL 3: DIE PERIODIEKE TEL VN ELEMENTE 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 e 9 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 l 27 1,8 14 Si 28 2,1 15 P 31 2,5 16 S 32 3,0 17 l 35,5 18 r 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 s 75 2,4 34 Se 79 2,8 35 r 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 g 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 a La 139 1,6 72 f Ta W Re Os Ir Pt u g 201 1,8 81 Tl 204 1,8 82 Pb 207 1,9 83 i 209 2,0 84 Po 2,5 85 t 86 Rn 0,7 87 Fr 0,9 88 Ra c 58 e Pr Nd Pm 62 Sm Eu Gd Tb Dy o Er Tm Yb Lu Th Pa 92 U Np 94 Pu 95 m 96 m 97 k 98 f 99 Es 100 Fm 101 Md 102 No 103 Lr Electronegativity Elektronegatiwiteit pproximate relative atomic mass enaderde relatiewe atoommassa tomic number toomgetal 29 u 63,5 1,9 Symbol Simbool KEY/SLEUTEL

18 Physical Sciences/P2 DE/Feb. Mar NS TLE 4: STNDRD REDUTION POTENTILS TEL 4: STNDRD-REDUKSIEPOTENSILE Increasing oxidising ability/toenemende oksiderende vermoë opyright reserved alf-reactions/alfreaksies E (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 r 2(l) + 2e 2r + 1,07 NO e NO(g) + 2 2O + 0,96 g e g(l) + 0,85 g + + e g + 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 l e l 1,66 Mg e Mg 2,36 Na + + e Na 2,71 a e a 2,87 Sr e Sr 2,89 a e a 2,90 s + + e - s - 2,92 K + + e K 2,93 Li + + e Li 3,05 Increasing reducing ability/toenemende reduserende vermoë

19 E Physical Sciences/P2 DE/Feb. Mar NS TLE 4: STNDRD REDUTION POTENTILS TEL 4: STNDRD-REDUKSIEPOTENSILE alf-reactions/alfreaksies (V) Li + + e Li 3,05 K + + e K 2,93 s + + e s 2,92 a e a 2,90 Sr e Sr 2,89 a e a 2,87 Na + + e Na 2,71 Mg e Mg 2,36 l e l 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 opyright reserved 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 g + + e g + 0,80 g e g(l) + 0,85 NO e NO(g) + 2 2O + 0,96 r 2(l) + 2e 2r + 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

20 Physical Sciences/P2 DE/Feb. Mar NS ENTRE NUMER: EXMINTION NUMER: QUESTION and in this GRP SEET with your NSWER OOK. 2,0 Graph of concentration versus time 1,5 oncentration (mol dm -3 ) 1,0 0, Time (minutes) opyright reserved