TRIAL EXAMINATION 2017

Transcription

1 GRDE 12 TIME: 3 HOURS MRKS: 150 WESTVILLE OYS HIGH PHYSIL SIENE TRIL EXMINTION 2017 PPER II EXMINERS: INTERNL MODERTOR: EXTERNL MODERTOR: N Julius; M ppenah; M llaway Pietersen & Mo ller D Hayes Moodley INSTRUTIONS ND INFORMTION nswer LL the questions in your answer book nswer Question 1 on one page. Start each subsequent question on a new page. Non-programmable calculators may be used. ppropriate mathematical instruments may be used. Number the answers correctly according to the numbering system used in this question paper. Data sheets and a periodic table are attached for your use. Give brief motivations, discussions, et cetera where required. ll numerical answers must be written correct to two decimal places. Write down your teacher s name and your name on both the answer book and question paper. Name Teacher s Name p1

2 QUESTION 1: MULTIPLE HOIE QUESTIONS Four possible answers, indicated by,, and D are given with each question. Each question has only one correct answer. Write down the numbers in a vertical column, in your answer book and next to each number write the letter of the correct answer H88 is an organic molecule. What is the name of the homologous series to which this compound belongs? Haloalkane lkane lkyne D lkene (2) 1.2 Which pair of compounds, at sea level, is arranged in order of DERESING vapor pressures? D H3OOH ; H3H2OH H3H2H2OH ; H3H2HO H3HO ; H3H2OH H3H2H3 ; H3H3 (2) 1.3 The diagram below shows the structural formula of a polymer which is used in the plastic industry. What is the IUP name of the monomer of which this polymer is composed? ethane ethene ethyne D ethanol (2) p2

3 1.4 onsider the chemical reaction represented by the chemical equation below. ao3(s) + 2Hl(aq) al2(aq) + O2(g) + H2O(l) Which one of the following changes will increase the RTE of production of carbon dioxide gas? Increase in pressure Increase in volume of Hl Increase in concentration of Hl D Decrease in volume of Hl (2) 1.5 The graph below shows a change made to a chemical equilibrium in a closed container at time t1. The chemical equation for the chemical reaction is given below. N2(g) + 3H2(g) 2NH3(g) ΔH < 0 H2 (g) oncentration (mol.dm -3 ) NH3 (g) N2 (g) t0 t1 Time (s) Which one of the following is the change made to the system at time t1? ddition of a catalyst Increase in temperature Increase in concentration of N2(g) D Increase in pressure by the decrease of the volume of the container (2) p3

4 1.6 hypothetical reaction reaches equilibrium in a closed container at a certain temperature. The following chemical equation represents this equilibrium: X2(g) + Y2(g) 2XY(g) ΔH < 0 Which ONE of the following changes to the equilibrium conditions will lead to an increase in the MOUNT of XY(g)? Decrease in temperature Increase in temperature Increase in pressure D Decrease in pressure (2) 1.7 Which ONE of the following is the correct description for a hydrochloric acid solution of concentration 0,10 mol.dm -3? Dilute strong acid Dilute weak acid oncentrated weak acid D oncentrated strong acid (2) 1.8 onsider the chemical reaction represented by the chemical equation below. H3PO4(aq) + HO3- (aq) H2PO4- (aq) + H2O3(aq) The ionization constant (Ka) for the acid is greater than 1 at 25 ⁰. The strongest SE in the above reaction is - H2PO4 - HO3 H3PO4 D H2O3 (2) p4

5 1.9 zinc plate is put into a copper(ii)sulphate solution. Which statement below, for the chemical reaction that occurs, is NOT correct? The zinc plate loses electrons and is the reducing agent. The copper ions gain electrons and are the oxidising agents. The copper ions gain electrons and are reduced. D The zinc plate gains mass and is reduced. (2) 1.10 The diagram below represents the membrane cell in the hlor-alkali industry. Gas Y Saturated Nal(aq) node athode Product X Which row in the table below gives the correct formulae for gas Y and product X? Gas Y Product X l2 NaOH H2 H2O l2 Nal D H2 NaOH (2) [20] p5

6 QUESTION 2: The capital letters to F in the table below represent six organic compounds. H l H H H H H H H H H3 H3 H2 H H3 O butan 1 ol D H3H(H3)H2H3 E H3 H3 H2 H H3 O F Pentanoic acid 2.1 To which homologous series do the following compounds belong to? (1) (1) 2.2 Write down the IUP name of compound D. (2) 2.3 Is compound a PRIMRY, SEONDRY or TERTIRY haloalkane? (1) 2.4 Organic compounds can be referred to as isomers Write down the letters of TWO compounds that are structural isomers of each other. (2) re the isomers in question RNHED, POSITIONL or FUNTIONL isomers? (1) 2.5 ompounds and F react in the presence of concentrated sulphuric acid Other than being a catalyst, state another function of the concentrated sulphuric acid for this reaction. (1) Write down the STRUTURL FORMUL and IUP NME for the organic product formed when compounds and F react. (3) [12] p6

7 QUESTION 3: n experiment was done to determine the boiling points of four different organic compounds (,, and D) from four different homologous series. The experiment was conducted under the same conditions for all four compounds. The table below shows the boiling points of the four organic compounds. OMPOUND OILING POINT ( 0 ) H3H2H2H3 1 H3H2H2HO 74,8 H3H2H2H2OH 117,7 D H3H2H2OOH 163,5 3.1 What is the dependent variable for this investigation? (1) 3.2 Write down the STRUTURL FORMUL for compound D. (2) 3.3 ompare the boiling points of compound and compound by making reference to the polarity of the molecules, the type and relative strengths of the intermolecular forces and energy involved. (4) 3.4 Would pentanal have a HIGHER or LOWER boiling point than compound? (1) 3.5 Explain why compound D has a higher boiling point than compound, in terms of molecular structure and the type and relative strengths of the intermolecular forces. (3) 3.6 Write down the letter of the organic compound with the LOWEST vapour pressure. Give a reason for your answer. (2) [13] p7

8 QUESTION 4: The flow diagram below shows five organic chemical reactions labelled I to V. X is an organic compound. Study the flow diagram and answer the questions that follow. propane II X + Hl I V III propene IV propan 1 ol 4.1 Write down a balanced chemical equation, using MOLEULR formula for reaction I. (3) 4.2 onsider reaction II What type of reaction is reaction II? Write down DDITION, SUSTITUTION or ELIMINTION. (1) Write down a reaction condition needed for this reaction to take place. (1) Write down the IUP NME and STRUTURL FORMUL of X. (3) 4.3 Write down the NME of a reactant that can react with X in reaction III. (1) 4.4 Reactions IV and V are both elimination reactions Write down the FORMUL of the catalyst used in reaction IV. (1) What is the name of the type of elimination reaction for reaction IV? (1) Reaction V takes place in the presence of concentrated potassium hydroxide. Write down a balanced chemical equation, using STRUTURL formula for reaction V. (4) [15] p8

9 QUESTION 5: You are asked to use the reaction between zinc granules and sulphuric acid to investigate ONE of the factors that affect reaction rates. The equation below represents the chemical reaction that takes place. Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g) You add 6,50 g of zinc granules to excess DILUTE sulphuric acid and then proceed to calculate the mass of zinc that reacted per unit time. The experiment is repeated but this time ONENTRTED sulphuric acid is reacted with the SME mass of zinc granules at the same initial temperature. 5.1 Define the term reaction rate of a chemical reaction. (2) 5.2 Give a reason why the acid must be in excess. (1) 5.3 Write down a hypothesis for this investigation. (2) 5.4 Give a reason why granules of zinc were used in both experiments. (1) The results obtained for the reaction using DILUTE sulphuric acid are represented in the graph below. 0,10 mount of Zn (mol) 0, Time (s) 5.5 Use the graph and calculate the mass of zinc that reacted between t = 0 s and t = 60 s. (4) 5.6 alculate the average rate of reaction, in g.s -1,during the first 60 s of the reaction. (2) 5.7 Redraw the graph above in your answer book and on the same set of axes use a DOTTED line to represent the curve that would be obtained if ONENTRTED sulphuric acid were used. No numerical values are required. (2) [14] p9

10 QUESTION 6: The reaction between hydrochloric acid and oxygen reaches equilibrium in a closed container according to the following balanced chemical equation: 4Hl(g) + O2(g) 2H2O(g) + 2l2(g) ΔH = 113 kj 6.1 Is this reaction EXOTHERMI or ENDOTHERMI? Give a reason for your answer. (2) 6.2 The graph below, not drawn to scale, shows how the amounts of reactants present in the container change with time at a specific temperature. The volume of the container is 5 dm 3. Use this graph to help you answer the following questions. Quantity (mol) 1,00 0,30 0,10 Hl(g) O2(g) 0 t1 t2 t3 time (s) How does the rate of the forward reaction at time t1 compare to that at time t2? Write down only GRETER THN, SMLLER THN or EQUL TO. Using the graph, give a reason for your answer. (2) How does the rate of the forward reaction compare to the rate of the reverse reaction at time t3? Write down only GRETER THN, SMLLER THN or EQUL TO. (1) alculate the equilibrium constant (Kc) for this reaction at this temperature. (9) 6.3 The temperature is now increased. How will this change affect the value of the equilibrium constant? Write down INRESE, DERESE or REMIN THE SME. (1) 6.4 Give an explanation for your answer to 6.3 above. (3) 6.5 How will each of the following changes affect the equilibrium concentration of the chlorine gas (l2)? Write down INRESE, DERESE or REMIN THE SME Water vapour is added to the container. (1) catalyst is added. (1) The volume of the container is increased, at constant temperature. (1) [21] p10

11 QUESTION 7: 7.1 Define an acid in terms of ronsted-lowry. (2) 7.2 Hydrochloric acid is a strong acid. Give a reason why Hydrochloric acid is regarded as a strong acid. (2) cm 3 of a 0,20 mol.dm -3 NaOH solution is titrated with a 0,30 mol.dm -3 Hl solution. The Hl is in the burette and the NaOH is in a conical flask. The diagram below represents the experimental set-up. burette Hl solution conical flask NaOH solution What apparatus would you use to measure exactly 30 cm 3 of NaOH into the conical flask, in this single burette titration method? (1) Name a suitable indicator that can show the end point of this titration. (2) Explain what is meant by the end point of this titration. (2) alculate the volume of the Hl solution that needs to be added to the NaOH solution to reach the end point of this titration? (5) In another titration 25 cm 3 of the 0,30 mol.dm -3 Hl solution is accidently added to 30 cm 3 of the 0,20 mol.dm -3 NaOH solution, in a conical flask. alculate the ph of the solution in the flask. (6) [20] p11

12 QUESTION 8: standard cell is constructed by connecting a Ni/Ni 2+ half cell to a Pt/H2/H + half cell. The sketch below represents this cell. V salt bridge Ni H2(g) Pt Ni 2+ (aq) H + (aq) 8.1 Give two reasons why Platinum (Pt) is used as an electrode in this cell. (4) 8.2 Which electrode is the anode? Write down either Ni or Pt. (1) 8.3 Give a reason for your answer to 8.2 above. (2) 8.4 Write down the NME of the oxidising agent in this cell. (1) 8.5 Write down a balanced ionic equation for the chemical reaction that takes place while this cell is functioning. (3) 8.6 This cell operates at a temperature of 25 o. Write down the OTHER TWO standard conditions which are applicable to this cell. (2) 8.7 Give one use of the salt bridge in a galvanic cell. (1) 8.8 alculate the initial emf of the cell under standard conditions. (3) 8.9 The concentration of the Ni 2+ solution is increased, while the other standard conditions are maintained. How will this change affect the value of the emf calculated in 8.8 above? Write down INRESES, DERESES or REMINS THE SME. (1) 8.10 Give an explanation for your answer to 8.9 above. (2) [20] p12

13 QUESTION 9: The electrochemical cell, illustrated below, is used to refine an impure copper rod. Electrodes and are connected to a cell. Electrolyte X 9.1 What energy conversion takes place in this electrochemical cell? (2) 9.2 Explain why a D (direct current) source is used this cell. (2) 9.3 Which electrode or is the IMPURE copper rod? (1) 9.4 Explain your choice to 9.3 above. Include a half reaction in your explanation. (3) 9.5 Write down the FORMUL or NME of electrolyte X used in this cell. (2) 9.6 Give a reason why the concentration of electrolyte X remains constant during the process of refining. (2) 9.7 The impure copper contains small quantities of silver. Use the standard electrode potentials table to explain why these small quantities of silver will not affect this refining process. (3) [15] TOTL: 150 p13