NATIONAL SENIOR CERTIFICATE GRADE 11

Transcription

1 NTIONL SENIOR ERTIFITE GRE 11 PHYSIL SIENES: HEMISTRY (P2) NOVEMER 2015 MRKS: 150 TIME: 3 hours This question paper consists of 13 pages, 4 data sheets and 1 answer sheet.

2 Physical Sciences/P2 2 E/November 2015 PS Grade 11 INSTRUTIONS N INFORMTION Write your name and class (for example 11) in the appropriate spaces on the NSWER OOK. This question paper consists of TEN questions. nswer QUESTION 4.2 and QUESTION 4.3 on the attached NSWER SHEET. nswer LL the other questions in the NSWER OOK. Start EH 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 T SHEETS. 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.

3 Physical Sciences/P2 3 E/November 2015 NS Grade 11 QUESTION 1: MULTIPLE-HOIE 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 ( ) next to the question number ( ) in the NSWER OOK, for example 1.11 E. 1.1 ccording to the rrhenius theory, all bases are proton donors. are proton acceptors. form H 3 O + ions in solution. form OH ions in solution. (2) The number of neutrons in an atom of 7 N is (2) 1.3 Which ONE of the following has the strongest forces between its molecules? F 2 l 2 r 2 I 2 (2) 1.4 Which ONE of the following has a tetrahedral shape? + H 3 O + NH 4 O 2 ll 3 (2)

4 Physical Sciences/P2 4 E/November 2015 NS Grade Two moles of H 2 gas at STP occupy a volume of... 2 dm 3 11,2 dm 3 22,4 dm 3 44,8 dm 3 (2) 1.6 Which ONE of the following statements ORRETLY describes the characteristics of an endothermic reaction? ΔH is positive and the products have less potential energy than the reactants. ΔH is positive and the products have more potential energy than the reactants. ΔH is negative and the products have less potential energy than the reactants. ΔH is negative and the products have more potential energy than the reactants. (2) 1.7 Which ONE of the following balanced equations represents a redox reaction? H + (aq) + OH - (aq) H 2 O(l) Mg(s) + uso 4 (aq) u(s) + MgSO 4 (aq) 2Nal(aq) + Pb(NO 3 ) 2 (aq) 2NaNO 3 (aq) + Pbl 2 (s) H 2 SO 4 (aq) + a(no 3 ) 2 (aq) aso 4 (s) + 2HNO 3 (aq) (2) 1.8 uring the extraction of gold, zinc powder is added to a solution of gold cyanide to produce gold according to the following balanced equation: Zn(s) + 2Nau(N) 2 (aq) 2u(s) + Zn(N) 2 (aq) + 2NaN(aq) The oxidising agent in this reaction is... u + Zn Na + N (2)

5 Physical Sciences/P2 5 E/November 2015 NS Grade The volume of a gas at a certain temperature and pressure is V. If the temperature is doubled and the pressure is halved, the volume of the gas will be 4V 2V V ½V (2) 1.10 Two identical containers, M and N, are shown below. ontainer M contains H 2 (g) and container N contains O 2 (g). oth gases are at a temperature of 25 and a pressure of 101,3 kpa. M H 2 (g) ,3 kpa N O 2 (g) ,3 kpa onsider the following statements: (i) The average kinetic energy of the molecules is the same in both containers. (ii) ontainer M contains more gas molecules than container N. (iii) The mass of the gas in container N is greater than the mass of the gas in container M. Which of the above statements is/are ORRET? (i) only (iii) only (i) and (ii) only (i) and (iii) only (2) [20]

6 Physical Sciences/P2 6 E/November 2015 NS Grade 11 QUESTION 2 (Start on a new page.) Molecules such as O 2 and H 2 O are formed through covalent bonding. 2.1 efine the term covalent bonding. (2) 2.2 ONE of the above molecules has lone pairs of electrons on the central atom. raw the Lewis diagram for this molecule. (2) 2.3 H 3 O + is formed when H 2 O forms a dative covalent bond with an H + ion raw the Lewis diagram for H 3 O +. (1) State TWO conditions for the formation of such a bond. (2) 2.4 The polarity of molecules depends on the IFFERENE IN ELETRONEGTIVITY and the MOLEULR SHPE efine the term electronegativity. (2) alculate the difference in electronegativity between: (a) and O in O 2 (1) (b) H and O in H 2 O (1) Explain the difference in polarity between O 2 and H 2 O by referring to the polarity of the bonds and the shape of the molecules. (6) [17]

7 Physical Sciences/P2 7 E/November 2015 NS Grade 11 QUESTION 3 (Start on a new page.) 3.1 The boiling point of compounds to E are given in the table below. OMPOUN FORMUL OILING POINT ( ) H H H H E 20 H efine the term boiling point. (2) alculate the molecular mass of compound. (1) In what phase is compound at 25? (1) Name the type of intermolecular force present in compound. (1) Explain why the boiling point increases from compound to E. (3) How does the vapour pressure of compound compare to the vapour pressure of compound? Write down only HIGHER THN, LOWER THN or EQUL TO. (1) 3.2 onsider the boiling points of the compounds in the table below. SUSTNE OILING POINT ( ) H 2 S 60 NH 3 33 H 2 O Which ONE of the substances in the table above has the weakest forces between its molecules? (1) Name the type of intermolecular force found between NH 3 molecules. (1) Explain the following statement: lthough the shape of the molecules of H 2 S and H 2 O is similar, there is a remarkable difference in their boiling points. (4) [15]

8 Physical Sciences/P2 8 E/November 2015 NS Grade 11 QUESTION 4 (Start on a new page.) learner investigates the relationship between the pressure and volume of an enclosed ITOMI gas at 25. He records the volume of the gas for different pressures in the table below. PRESSURE (kpa) VOLUME (cm 3 ) 1 (cm -3 ) V , , (a) (b) 4.1 Write down the name of the gas law being investigated. (1) nswer QUESTION 4.2 and QUESTION 4.3 on the attached NSWER SHEET Two values in the table, (a) and (b), have not been calculated. V alculate these values. (1) 4.3 raw a graph of pressure versus V 1 on the attached NSWER SHEET. (4) 4.4 Use the graph to determine the volume of the gas at 68 kpa. (2) 4.5 The mass of the enclosed ITOMI gas is 2,49 x 10-2 g Use the conditions at a pressure of 100 kpa and calculate the molar mass of the enclosed gas. (6) Write down the molecular formula of the enclosed gas. (1) 4.6 The sketch graph below shows the relationship between volume and temperature for an ideal gas. Volume (cm 3 ) Temperature (K) Redraw the above graph in the NSWER OOK. On the same set of axes, use a ROKEN LINE to sketch the graph that will be obtained for the diatomic gas above. (1) Fully explain why this diatomic gas deviates from ideal behaviour. (3) [19]

9 Physical Sciences/P2 9 E/November 2015 NS Grade 11 QUESTION 5 (Start on a new page.) The fizz produced when an antacid dissolves in water is caused by the reaction between sodium hydrogen carbonate (NaHO 3 ) and citric acid (H 3 6 H 5 O 7 ). The balanced equation for the reaction is: 3NaHO 3 (aq) + H 3 6 H 5 O 7 (aq) Na 3 6 H 5 O 7 (aq) + 3O 2 (g) + 3H 2 O(l) 5.1 Write down the FORMUL of the substance that causes the fizz when the antacid dissolves in water. (1) certain antacid contains 1,8 g of H 3 6 H 5 O 7 and 3,36 g of NaHO 3. The antacid is dissolved in 100 cm 3 distilled water in a beaker. 5.2 efine 1 mole of a substance. (2) 5.3 alculate the number of moles of NaHO 3 in the antacid. (3) 5.4 etermine, using calculations, which substance is the limiting reagent. (4) 5.5 alculate the mass of the reactant in excess. (3) 5.6 alculate the mass decrease of the beaker contents on completion of the reaction. (3) [16] QUESTION 6 (Start on a new page.) 6.1 Sodium thiosulphate, Na 2 S 2 O 3 (s), reacts with 200 cm 3 of a hydrochloric acid solution, Hl(aq), of concentration 0,2 mol dm -3 according to the following balanced equation: Na 2 S 2 O 3 (s) + 2Hl(aq) 2Nal(aq) + S(s) + SO 2 (g) + H 2 O(l) efine the term concentration of a solution. (2) alculate the number of moles of Hl(aq) added to the sodium thiosulphate. (3) alculate the volume of SO 2 (g) that will be formed if the reaction takes place at STP. (3)

10 Physical Sciences/P2 10 E/November 2015 NS Grade Menthol, the substance we can smell in mentholated cough drops, is composed of carbon (), hydrogen (H) and oxygen (O). uring combustion of a 9,984 g sample of menthol, it is found that 28,160 g of O 2 (g) and 11,520 g of H 2 O(g) is produced alculate the mass of carbon () in the O 2. (4) Use relevant calculations to determine the empirical formula of menthol. (7) The molar mass of menthol is 156 g mol -1. etermine the molecular formula of menthol. (2) [21] QUESTION 7 (Start on a new page.) barium hydroxide solution, a(oh) 2 (aq), reacts with a nitric acid solution, HNO 3 (aq), according to the following balanced equation: a(oh) 2 (aq) + 2HNO 3 (aq) a(no 3 ) 2 (aq) + 2H 2 O(l) The potential energy graph below shows the change in potential energy for this reaction. Potential energy (kj mol -1 ) 116 kj mol -1 ourse of reaction 7.1 Is this reaction ENOTHERMI or EXOTHERMI? Give a reason for the answer. (2) 7.2 Use energy values, and indicated on the graph and write down an expression for each of the following: The energy of the activated complex (1) The activation energy for the forward reaction (1) H for the reverse reaction (1) 7.3 alculate the amount of energy released during the reaction if 0,18 moles of a(oh) 2 (aq) reacts completely with the acid. (3) [8]

11 Physical Sciences/P2 11 E/November 2015 NS Grade 11 QUESTION 8 (Start on a new page.) When sulphuric acid reacts with water, it ionises in two steps, as shown in the two balanced equations below. I: H 2 SO 4 (aq) + H 2 O(l) H 3 O + (aq) + HSO 4 (aq) II: HSO 4 (aq) + H 2 O(l) H 3 O + (aq) + 2 SO 4 (aq) 8.1 efine an acid in terms of the Lowry-rønsted theory. (2) 8.2 Write down the FORMUL of: The conjugate base of The conjugate acid of HSO 4 (aq) (1) HSO 4 (aq) (1) substance that acts as ampholyte in these reactions (1) 8.3 few drops of bromothymol blue indicator are added to a potassium hydroxide solution in a beaker. dilute sulphuric acid solution is now gradually added to this solution until the colour of the indicator changes. Write down the: Type of reaction that takes place (Write down only REOX, PREIPITTION or NEUTRLISTION.) (1) alanced equation for the reaction that takes place (3) olour change of the indicator (2) NME of the salt formed in this reaction (1) [12]

12 Physical Sciences/P2 12 E/November 2015 NS Grade 11 QUESTION 9 (Start on a new page.) 9.1 Oxidation numbers make it easier to determine whether an element or a substance is oxidised or reduced during a chemical reaction efine the term oxidation with reference to oxidation numbers. (2) alculate the oxidation number of chromium in 2 r 2O 7. (1) alculate the oxidation number of oxygen in H 2 O 2. (1) 9.2 onsider the UNLNE equation below: Fe 2+ (aq) + l 2 (g) Fe 3+ (aq) + l efine the term reducing agent with reference to electron transfer. (2) From the above equation, write down the: FORMUL of the reducing agent (1) FORMUL of the oxidising agent (1) Reduction half-reaction (2) Oxidation half-reaction (2) alanced net redox reaction (2) [14]

13 Physical Sciences/P2 13 E/November 2015 PS Grade 11 QUESTION 10 (Start on a new page.) The simplified diagram below shows a blast furnace used for the extraction of iron from iron ore. P represents a reactant added to the blast furnace. Q and R represent products that leave the blast furnace. Waste gases out Raw materials Iron ore Limestone oke Waste gases out P R Q Limestone and coke are added to the blast furnace, as shown in the diagram above. Write down the function of: Limestone oke (1) (1) 10.2 Write down the NME of the substance represented by: P Q R (1) (1) (1) 10.3 Write down the NME or FORMUL of ONE waste gas formed during the extraction of iron from iron ore. (1) 10.4 The balanced equation for the extraction of iron from iron ore is: Write down the: Fe 2 O 3 (s) + 3O(g) 2Fe(s) + 3O 2 (g) Function of carbon monoxide in this reaction (1) FORMUL of the substance that is reduced (1) [8] TOTL: 150

14 Physical Sciences/P2 E/November 2015 PS Grade 11 T FOR PHYSIL SIENES GRE 11 PPER 2 (HEMISTRY) GEGEWENS VIR FISIESE WETENSKPPE GR 11 VRESTEL 2 (HEMIE) TLE 1: PHYSIL ONSTNTS/TEL 1: FISIESE KONSTNTES NME/NM SYMOL/SIMOOL VLUE/WRE vogadro's constant vogadro-konstante N 6,02 x mol -1 Molar gas constant Molêre gaskonstante R 8,31 J K -1 mol -1 Standard pressure Standaarddruk θ p 1,013 x 10 5 Pa Molar gas volume at STP Molêre gasvolume by ST V m 22,4 dm 3 mol -1 Standard temperature Standaardtemperatuur θ T 273 K TLE 2: FORMULE/TEL 2: FORMULES p V p V = pv = nrt T1 T2 m n= M V n= V m n= N N n c = OR/OF V m c = MV

15 Physical Sciences/P2 E/November 2015 PS Grade 11 TLE 3: THE PERIOI TLE OF ELEMENTS/TEL 3: IE PERIOIEKE TEL VN ELEMENTE 1 (I) 2 (II) (III) 14 (IV) 15 (V) 16 (VI) 17 (VII) 18 (VIII) 2,1 1 H 1 2 He 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 Hf Ta W Re Os Ir Pt u Hg 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 y Ho 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 pproximate relative atomic mass enaderde relatiewe atoommassa tomic number toomgetal 29 u 63,5 1,9 Symbol Simbool Electronegativity Elektronegatiwiteit KEY/SLEUTEL

16 Physical Sciences/P2 E/November 2015 PS Grade 11 Increasing oxidising ability/toenemende oksiderende vermoë θe TLE 4: STNR REUTION POTENTILS TEL 4: STNR-REUKSIEPOTENSILE Half-reactions/Halfreaksies (V) F 2(g) + 2e 2F + 2,87 o 3+ + e o ,81 H 2O 2 + 2H + +2e 2H 2O +1,77 MnO 4 + 8H+ + 5e Mn H 2O + 1,51 l 2(g) + 2e 2l + 1,36 r 2O H+ + 6e 2r H 2O + 1,33 O 2(g) + 4H + + 4e 2H 2O + 1,23 MnO 2 + 4H + + 2e Mn H 2O + 1,23 Pt e Pt + 1,20 r 2(l) + 2e 2r + 1,07 NO 3 + 4H+ + 3e NO(g) + 2H 2O + 0,96 Hg e Hg(l) + 0,85 g + + e g + 0,80 NO 3 + 2H+ + e NO 2(g) + H 2O + 0,80 Fe 3+ + e Fe ,77 O 2(g) + 2H + + 2e H 2O 2 + 0,68 I 2 + 2e 2I + 0,54 u + + e u + 0,52 SO 2 + 4H + + 4e S + 2H 2O + 0,45 2H 2O + O 2 + 4e 4OH + 0,40 u e u + 0,34 SO 4 + 4H+ + 2e SO 2(g) + 2H 2O + 0,17 u 2+ + e u + + 0,16 Sn e Sn ,15 S + 2H + + 2e H 2S(g) + 0,14 2H + + 2e H 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 2H 2O + 2e H 2(g) + 2OH 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

17 Physical Sciences/P2 E/November 2015 PS Grade 11 TLE 4: STNR REUTION POTENTILS TEL 4: STNR-REUKSIEPOTENSILE Increasing oxidising ability/toenemende oksiderende vermoë 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 2H 2O + 2e H 2(g) + 2OH 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 0,06 2H + + 2e H 2(g) 0,00 S + 2H + + 2e H 2S(g) + 0,14 Sn e Sn ,15 u 2+ + e u + + 0,16 SO 4 + 4H+ + 2e SO 2(g) + 2H 2O + 0,17 u e u + 0,34 2H 2O + O 2 + 4e 4OH + 0,40 SO 2 + 4H + + 4e S + 2H 2O + 0,45 u + + e u + 0,52 I 2 + 2e 2I + 0,54 O 2(g) + 2H + + 2e H 2O 2 + 0,68 Fe 3+ + e Fe ,77 NO 3 + 2H+ + e NO 2(g) + H 2O + 0,80 g + + e g + 0,80 Hg e Hg(l) + 0,85 NO 3 + 4H+ + 3e NO(g) + 2H 2O + 0,96 r 2(l) + 2e 2r + 1,07 Pt e Pt + 1,20 MnO 2 + 4H + + 2e Mn H 2O + 1,23 O 2(g) + 4H + + 4e 2H 2O + 1,23 r 2O H+ + 6e 2r H 2O + 1,33 l 2(g) + 2e 2l + 1,36 MnO 4 + 8H+ + 5e Mn H 2O + 1,51 H 2O 2 + 2H + +2 e 2H 2O +1,77 o 3+ + e o ,81 F 2(g) + 2e 2F + 2,87 Increasing reducing ability/toenemende reduserende vermoë

18 Physical Sciences/P2 E/November 2015 PS Grade 11 NME: LSS: QUESTION 4.2 and 4.3 Submit this NSWER SHEET with the NSWER OOK. PRESSURE (kpa) VOLUME (cm 3 ) 1 (cm -3 ) V , , Graph of pressure versus V Pressure (kpa) ,02 0,04 0,06 0,08 0,1 1 (cm -3 ) V