SENIOR CERTIFICATE EXAMINATIONS

Transcription

1 SENIOR ERTIFITE EXMINTIONS PYSIL SIENES: EMISTRY (P2) 2017 MRKS: 150 TIME: 3 hours This question paper consists of 15 pages and 4 data sheets.

2 Physical Sciences/P2 2 E/2017 INSTRUTIONS N INFORMTION Write your examination number and centre number in the appropriate spaces on the NSWER OOK. This question paper consists of TEN questions. 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 T SEETS. Show LL formulae and substitutions in LL calculations. Round off your FINL 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/2017 QUESTION 1: MULTIPLE-OIE QUESTIONS Various options are provided as possible answers to the following questions. Write down the question number ( ), choose the answer and make a cross (X) over the letter ( ) of your choice in the NSWER OOK. EXMPLE: The boiling point of a compound is the minimum temperature at which it boils. average temperature at which it boils across all possible atmospheric pressures. maximum temperature at which it boils. temperature at which its vapour pressure equals atmospheric pressure. (2) 1.2 Which ONE of the following organic reactions will take place only when exposed to light? l 2 2 l 2 l l l + l (2) 1.3 The energy change during a chemical reaction is known as bond energy. heat of reaction. activation energy. activated complex. (2)

4 Physical Sciences/P2 4 E/ Which ONE of the descriptions below is TRUE for a chemical reaction in equilibrium? ONENTRTIONS OF RETNTS N PROUTS FORWR N REVERSE RETION RTES Remain constant Equal Remain constant Not equal Equal Equal Not equal Not equal (2) 1.5 The complete combustion of ethane is represented by the balanced equation below (g) + 7O 2 (g) 4O 2 (g) O(g) The maximum volume of gas that can be produced by the complete combustion of 100 cm 3 of ethane is: 200 cm cm cm cm 3 (2) 1.6 The reaction below reaches equilibrium in a closed container. N 2 (g) (g) 2N 3 (g) + energy onsider the following statements regarding the equilibrium above: I: When one N 2 molecule combines with three 2 molecules, two N 3 molecules decompose at the same time. II: n iron oxide catalyst increases the amount of ammonia produced in this reaction. III: When the temperature increases, the equilibrium constant (K c ) for this reaction will increase. Which of the above statements is/are ORRET? I only I and II only I and III only I, II and III (2)

5 Physical Sciences/P2 5 E/ Which ONE of the following pairs represents the conjugate acid and the conjugate base of PO? 2 4 ONJUGTE I PO 3 4 2PO 4 ONJUGTE SE 2PO 4 3 PO 4 2PO 4 3 PO 4 2 2PO 4 2 PO 4 (2) 1.8 simplified diagram for the extraction of aluminium is shown below. O 2 (g) Graphite electrode Electrolyte Molten aluminium onsider the following statements regarding the process above: I: The electrolyte is a mixture of cryolite and aluminium oxide. II: O 2 (g) is produced at the anode. III: The half-reaction at the cathode is l 3+ (aq) + 3e - l(s). Which of the above statements are ORRET? I and II only II and III only I and III only I, II and III (2)

6 Physical Sciences/P2 6 E/ Which ONE of the half-cells below will result in the IGEST emf when it is used as a cathode, together with a zinc half-cell as anode, in a standard galvanic cell? u 2+ (aq) u(s) Fe 2+ (aq) Fe(s) g + (aq) g(s) Sn 2+ (aq) Sn(s) (2) 1.10 Which of the following processes are LL involved in the preparation of ammonium sulphate? Ostwald process ontact process aber process Fractional distillation of liquid air Fractional distillation of liquid air Fractional distillation of liquid air Ostwald process aber process aber process ontact process ontact process Ostwald process (2) [20]

7 Physical Sciences/P2 7 E/2017 QUESTION 2 (Start on a new page.) 2.1 efine the term functional group of organic compounds. (2) 2.2 Write down the: Structural formula of the functional group of aldehydes (1) Name of the functional group of carboxylic acids (1) 2.3 The IUP name of an organic compound is 2,4-dimethylhexan-3-one. For this compound, write down the: omologous series to which it belongs (1) Structural formula (3) 2.4 Write down the IUP names of the following compounds: r (3) (2) [13]

8 Physical Sciences/P2 8 E/2017 QUESTION 3 (Start on a new page.) The boiling points of some organic compounds are given in the table below. Y represents an unknown boiling point. OMPOUN OILING POINT ( ) Methanol 64,7 Ethanol 78,3 Propan-1-ol 97,2 utan-1-ol 117,7 E utan-2-ol 99,5 F 2-methylpropan-1-ol Y G 2-methylpropan-2-ol 82,5 3.1 For the compounds listed above, write down the: Structural formula of compound F (3) LETTER that represents a POSITIONL isomer of compound E (1) LETTER that represents a IN isomer of compound E (1) 3.2 The boiling points increase from compound to compound Give a reason for this increase in terms of the molecular structure. (1) Name the intermolecular force in these compounds responsible for this increase. (1) 3.3 onsider the boiling points given below From these boiling points, choose the boiling point represented by Y in the table above. (1) Fully explain how you arrived at the answer to QUESTION (4) 3.4 ydrogen bonding is responsible for the relatively high boiling points of compounds to G in comparison with hydrocarbons of similar molecular size. raw TWO structural formulae of compound. Use a dotted line to show the hydrogen bonding between the two structural formulae. (2) 3.5 ompound reacts with propanoic acid in the presence of concentrated sulphuric acid. Write down the: Type of reaction that takes place (1) Structural formula of the organic product formed (2) [17]

9 Physical Sciences/P2 9 E/2017 QUESTION 4 (Start on a new page.) The flow diagram below shows how an alkene can be used to prepare other organic compounds. The letters to G represent different organic reactions. ompound Y l G Propane E 2 O n alcohol (major product) r F ompound X (major product) 4.1 Write down the type of reaction represented by: E (1) (1) (1) 4.2 Write down the IUP name of compound X. (2) 4.3 For reaction, write down: The type of elimination reaction (1) TWO reaction conditions (2) 4.4 Write down the: FORMUL of an inorganic reactant needed for reaction F (1) alanced equation, using structural formulae, for reaction G (4) [13]

10 Physical Sciences/P2 10 E/2017 QUESTION 5 (Start on a new page.) The apparatus below is used to investigate one of the factors that affects the rate of decomposition of hydrogen peroxide, 2 O 2. The balanced equation for the reaction is: 2 2 O 2 (aq) 2 2 O(l) + O 2 (g) Two experiments are conducted. The reaction conditions are as follows: Experiment I: Experiment II: 50 cm 3 of hydrogen peroxide is allowed to decompose at cm 3 of hydrogen peroxide decompose at 30 in the presence of copper(ii) oxide powder (uo). Graduated syringe Graduated syringe onical flask 2 O 2 (aq) uo(s) Experiment I Experiment II The results of the investigation are summarised in the table below. Experiment Total volume of O 2 Time taken for complete produced (dm 3 ) decomposition (min.) I 0,4 12,3 II 0,4 5,8 5.1 For this investigation, write down the function of the: Graduated syringe (1) opper(ii) oxide (1) 5.2 ow will you know when the reaction is completed? (1) 5.3 Write down the independent variable for this investigation. (1) 5.4 Use the collision theory to fully explain the difference in reaction rates of experiment I and experiment II. (3)

11 Physical Sciences/P2 11 E/ The graphs below show changes in the potential energy during the decomposition of hydrogen peroxide in experiment I and experiment II. Potential energy (kj) 2 O 2 2 O+ O 2 ourse of reaction Is energy SORE or RELESE during this reaction? Give a reason for the answer. (2) Which ONE of the curves, or, represents experiment II? (1) 5.6 alculate the rate, in mol dm -3 min -1, at which 50 cm 3 of hydrogen peroxide decomposes in experiment II. ssume that 1 mole of gas occupies a volume of 25 dm 3 at 30. (6) [16] QUESTION 6 (Start on a new page.) 6.1 onsider the balanced equation for a reversible reaction below. N 2 (g) + O 2 (g) 2NO(g) What is meant by the term reversible reaction? (1) The sketch graph below shows the relationship between the value of the equilibrium constant (K c ) for this reaction and temperature. K c Temperature Is the reaction ENOTERMI or EXOTERMI? (1) Fully explain the answer to QUESTION (3)

12 Physical Sciences/P2 12 E/2017 ow will E of the following changes affect the amount of NO(g) at equilibrium? hoose from INRESES, ERESES or REMINS TE SME More N 2 (g) is added. (1) The pressure is increased by decreasing the volume. (1) 6.2 Initially 336 g titanium (Ti) and 426 g chlorine gas (l 2 ) are mixed in a sealed 2 dm 3 container at a certain temperature. The reaction reaches equilibrium according to the following balanced equation: Ti(s) + 2l 2 (g) Til 4 (s) t equilibrium it is found that 288 g titanium is left in the container alculate the equilibrium constant (K c ) for the reaction at this temperature. (8) More titanium is now added to the equilibrium mixture. ow will this change affect the yield of Til 4 (s)? QUESTION 7 (Start on a new page.) hoose from INRESES, ERESES or REMINS TE SME. (1) [16] 7.1 Ethanoic acid ( 3 OO) is an acid that ionises incompletely in water according to the following balanced equation: 3 OO(aq) + 2 O(l) 3 OO (aq) + 3 O + (aq) Write down the term used for the underlined phrase above. (1) n ethanoic acid solution has a p of 4 at 25. alculate the concentration of the hydronium ions, 3 O + (aq) in the solution. (3) 7.2 standard solution of potassium hydroxide (KO) is prepared in a 250 cm 3 volumetric flask. uring a titration, 12,5 cm 3 of this solution neutralises 25 cm 3 of a 0,16 mol dm -3 ethanoic acid solution. The balanced equation for the reaction is: 3 OO(aq) + KO(aq) 3 OOK(aq) + 2 O(l) efine a base according to the rrhenius theory. (2) alculate the mass of potassium hydroxide used to prepare the solution above in the 250 cm 3 volumetric flask. (7) Will the p of the solution in the conical flask at the end point be GRETER TN 7, SMLLER TN 7 or EQUL TO 7? (1) Explain the answer to QUESTION with the aid of a balanced chemical equation. (3) [17]

13 Physical Sciences/P2 13 E/2017 QUESTION 8 (Start on a new page.) The electrochemical cell represented by the cell notation below is used to investigate the relationship between the concentration of X 2+ (aq) and the emf of the cell. The concentration of Zn 2+ (aq) and the temperature are kept at standard conditions. Zn(s) Zn 2+ (aq) X 2+ (aq) X(s) The graph below shows the results obtained. Graph of emf versus [X 2+ ] 1,11 1,09 emf (V) 1,08 1,07 0,1 0,2 0,6 1,0 [X 2+ ] (mol dm -3 ) 8.1 For this investigation, write down the: ependent variable (1) Name of an instrument needed to measure the emf of the cell (1) Name of the component of the cell that ensures electrical neutrality (1) Values of TWO standard conditions needed to ensure that the standard emf is obtained (2) 8.2 Write down the conclusion that can be drawn from the results. (2) 8.3 Identify electrode X with the aid of a calculation. (5) 8.4 Write down the overall (net) cell reaction that takes place when this cell is in operation. (3) [15]

14 Physical Sciences/P2 14 E/2017 QUESTION 9 (Start on a new page.) The simplified diagram below represents a cell used to electroplate an iron medal with a thin layer of gold. battery P ul 3 (aq) Medal 9.1 Is this an ELETROLYTI or a GLVNI cell? (1) 9.2 Which electrode, P or the Medal, is the anode? (1) 9.3 Write down the: alf-reaction that takes place at electrode P (2) Oxidation number of gold (u) in the electrolyte (1) Energy change that takes place in this cell (1) Visible change that occurs on electrode P after the cell functions for a while (1) 9.4 esides improving appearance, state ONE other reason why the medal is electroplated. (1) 9.5 State ONE of the two possible changes that should be made to the cell above to electroplate the medal with silver instead of gold. (1) [9]

15 Physical Sciences/P2 15 E/2017 QUESTION 10 (Start on a new page.) 10.1 The letters to F in the table below represent some fertilisers and raw materials used in the preparation of fertilisers. Sulphur ir Methane Potassium chloride E mmonium sulphate F mmonium nitrate Write down the: LETTERS representing TWO raw materials used in the preparation of compound F (2) NME or FORMUL of the acid needed to prepare compound F (1) LETTER representing the solid raw material used in the contact process (1) alanced equation for the preparation of compound E (3) LETTER representing the raw material that supplies the primary nutrient needed for development of flowers (1) kg bag of fertiliser is labelled as follows: alculate the mass of the: 2 : 3 : 2 (22) Phosphorous in the bag (3) Filler in the bag (3) [14] TOTL: 150

16 Physical Sciences/P2 1 E/2017 T FOR PYSIL SIENES GRE 12 PPER 2 (EMISTRY) GEGEWENS VIR FISIESE WETENSKPPE GR 12 VRESTEL 2 (EMIE) TLE 1: PYSIL ONSTNTS/TEL 1: FISIESE KONSTNTES NME/NM SYMOL/SIMOOL VLUE/WRE Standard pressure Standaarddruk 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 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 = V cava c v b n or/of m c = MV n= n= a = p = -log[ b n 3 O + ] b K w = [ 3 O + ][O - ] = 1 x at/by 298 K N N V V m E cell = E E / E = E E cathode anode sel katode anode or/of E = E E / E = E E cell reduction oxidation sel reduksie oksidasie or/of E = E E / E = E E cell oxidising agent reducing agent sel oksideermiddel reduseermiddel

17 Physical Sciences/P2 2 E/2017 TLE 3: TE 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, 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 y 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 3 E/2017 TLE 4: STNR REUTION POTENTILS TEL 4: STNR-REUKSIEPOTENSILE Increasing oxidising ability/toenemende oksiderende vermoë 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 4 E/2017 TLE 4: STNR REUTION POTENTILS TEL 4: STNR-REUKSIEPOTENSILE 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 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