Centre NumberSurnameOther namesCandidate Number AHS Examinations Semester 4ChemistryAdvanced LevelUnit 4: General Principles of y I , Equilibria and Further Organic Chemistry (including synoptic assessment)April 2012 Time: 1 hour 40 minutesWrite your name herePaper Reference6CH04/01You do not need any other materials.Total MarksGrade

General Principles of Chemistry I Rates , Equilibria and Further Organic Chemistry (including synoptic assessment)

InstructionsUse black ink or ball-point pen. Fill in the boxes at the top of this page with your name, centre number and candidate number. Answer all questions. Answer the questions in the spaces provided there may be more space than you need.InformationThe total mark for this paper is 90. The marks for each question are shown in brackets use this as a guide as to how much time to spend on each question. Questions labelled with an asterisk (*) are ones where the quality of your written communication will be assessed you should take particular care with your spelling, punctuation and grammar, as well as the clarity of expression, on these questions. A data booklet is provided with this paper.AdviceRead each question carefully before you start to answer it. Keep an eye on the time. Try to answer every question.Check your answers if you have time at the end. Check your answer if you have time at the end.

A37964H2012 Addu High School.

SECTION AAnswer ALL questions.

For questions 110, in Section A, select one answer from A to D and put a cross in the box .

If you change your mind, put a line through the box and then mark your

new answer with a cross .1. 1,2-dibromoethane reacts with potassium iodide dissolved in methanol according to the equation:C2H5Br + OH C2H5OH + BrThe rate equation for this reaction is (1) Arate = k[C2H5Br]1[OH]1B rate = k[C2H5Br] 1 Crate = k[OH]1D rate = k[C2H5Br] 0[OH]02. For an exothermic chemical process occurring in two steps as (1)A + B X (slow); X AB (fast) The progress of the reaction can be best described by 3. Propanone reacts with iodine in acidic solution as shown in the equation below.CH3COCH3 (aq) + I2 (aq) CH3COCH2I(aq) + H+ (aq) + I (aq) The rate equation for the reaction isRate = k[CH3COCH3 (aq)]1[H+(aq)] 1 [I2 (aq)]0When the concentrations of all three reactants are doubled, the rate will increase by a factor of (1) A 2 B 4 C 6 D 164. Which one of the following statements is not correct? (1) A. When H for a reaction is negative, the reaction is never spontaneous. B. When S for a reaction is positive, the reaction is spontaneous. C When G for a reaction is negative, the reaction is spontaneous. D When S for a reaction is zero, the system is at equilibrium 5. Solutions of concentration 0.1 mol dm3 of iron(II) ions and silver(I) ions were mixed at room temperature and allowed to reach equilibrium.Fe2+(aq) + Ag+(aq) Fe3+(aq) + Ag(s) Which one of the following statements is true? (1)A as the equilibrium position was approached, the forward reaction became slower until it stopped.B at the equilibrium position, no more Ag(s) reacted with Fe3+(aq).C at the equilibrium position, the rate of the forward reaction equalled the rate of the backward reaction.D no Fe3+(aq) reacted with Ag(s) until the equilibrium position was reached6. For the equilibrium,N2(g) + 3H2(g) 2NH3(g) Which is the correct expression for Kp? (1) [NH3(g)] 2 p2 (NH3(g)) A B [N2(g)]1[H2(g)]3 p1(N2(g)) p3(H2(g))

[N2(g)]1 [H2(g)]3 p1(N2(g)) p3(H2(g)) C D [NH3(g)]2 p2 (NH3(g))7. Which one of the following would be expected to change the value of the equilibrium constant? (1) A adding reactant B adding product C changing the temperature D adding a catalyst8. Given that the ionic product of water at 25 C the value of Kw is 1.00 x 1014 mol2 dm6. (1) Calculate the pH of a 0.001 mol dm3 solution of KOH A 11 B 14 C 3 D 5 9. This question concerns the titration of a solution of sodium hydroxide with a solution of hydrochloric acid. As the titration proceeds the pH of the mixture changes.(a) What was the pH when 25.05 cm3 of 1.00 mol dm3 NaOH(aq) had been added to 25 cm3 of 1.00 mol dm3 HCl(aq)? (1) A 3 B 6 C 8 D11(b) Which one of the following indicators would be most suitable to use to determine the end point of this titration? (1) pH range pH range A methyl violet 01.6 B universal indicator 3 11 C thymolphthalein 8.310.6 D alizarin yellow R 10.1 13.010. Titration curves labelled A, B, C and D for combinations of different acids and bases are shown below. All solutions have a concentration of 0.1 mol dm3.

Select from A, B, C and D the curve produced by the addition of(a) ammonia to 25 cm3 of hydrochloric acid (1) A BC D(b) ethanoic acid to 25 cm3 of sodium hydroxide (1) A BC D(c) sodium hydroxide to 25 cm3 of hydrochloric acid (1)A BC D

11. This question concerns four solutions, A to D. They were prepared by mixing equal volumes of 0.2 mol dm3 solutions of two different substances. The substances were AHCl(aq) and NaOH(aq) BHCl(aq) and NaCl(aq) CNH3(aq) and NH4Cl(aq)DCH3COOH(aq) and CH3CO2Na(aq) Select, from A to D, the mixture which would:(a) have the lowest concentration of hydrogen ions (1) A BC D(b) act as a buffer of pH about 5 (1) A BC D12. Which of the following compounds has both optical and E-Z isomers? (1) A CH3CH=CHCH2CH3 B CH3CHClCH=C(CH3)2 C CH3CCl=CClCH3 D CH3CHBrCH=CHCl13. This question concerns the nucleophilic addition reaction between a carbonyl compoundand hydrogen cyanide, HCN.(a) Which one of the following carbonyl compounds would not produce a racemic mixture? A CH3COCH3 B C2H5CHO C HCHO D C2H5COC2H5(1)(b) Which of the following best represents the first step of the mechanism for this reaction with an aldehyde? (1) 14. This question concerns a proposed two-stage synthetic route to prepare butanamide, CH3CH2CH2CONH2 NH3 Carboxylic acid Acyl chloride butanamide (a) A suitable starting material for this preparation would have the formula (1) A CH3CH2CH2 CH2OH B CH3CH2CH2OH C CH3CH2CH2COOH D CH3CH2COCH3(b) Which of the following reagents is needed to convert the carboxylic acid into the acyl chloride? (1) A chlorine B phosphorus(V) chloride C hydrogen chloride D ethanoyl chloride (Total for section A = 20 Marks) SECTION B

Answer ALL questions. Answer the questions in the space provided. 15. In an experiment to determine the rate of the reaction between persulphate ions and iodide ions in aqueous solutionS2O+ 2I 2SO+ I2 The following data were obtained:

(a) (i)Deduce the order of reaction with respect to each of the reagents and hence write the rate equation for the reaction. (3) Working:------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Rate equation:-

---------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------

(ii) With reference to this reaction state what is meant by the overall order of a reaction. (1) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (iii)Calculate the rate constant including units. (2) Calculation :

Unit:---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (iv) Explain why the rate equation cannot be written directly from the stoichiometric equation for the reaction. (1) (1) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (i)Suggest a suitable experimental technique that would enable you to determine the rate of the reaction given opposite. (1)

---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (ii)Suggest a necessary condition that would help to ensure accurate results. (1)

---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (iii)Suggest one advantage or disadvantage of your chosen experimental method. (1)

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(Total For Question 15 = 10 marks)

16. When barium nitrate is heated it decomposes as follows: Ba(NO3)2(s) BaO(s) + 2NO2(g) + O2(g)H = +505.0 kJ mol1(a)Use the following data when answering this part of the question.SubstanceStandard entropy,S / J mol1 K1

Ba(NO3)2(s)+ 213.8

BaO(s)+ 70.4

NO2(g)+ 240.0

O2(g)+ 205.0

(i)Explain why: S [NO2(g)] is greater than S [BaO(s)] (1) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- S [Ba(NO3)2(s)] is greater than S [BaO(s)]. (1)---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (ii)Calculate the entropy change of the system, Ssystem, for this reaction. Include a sign and units in your answer. (2)

(b)Calculate the entropy change of the surroundings, Ssurroundings, for the reaction at 298 K. Include a sign and units in your answer. (2)

(c) Calculate Stotal, and explain the significance of the sign for this value. (2)

(d) Calculate the minimum temperature at which the decomposition of barium nitrate should occur. You can assume that H and Ssystem are not affected by a change in temperature. (2)

(Total For Question 16 = 10 marks)

17. (a) The first stage in the manufacture of sulphuric acid is the Contact Process.2SO2 + O2 2SO3 H = -196kJAt 400 C the equilibrium constant Kp = 3.00 104 atm1. A catalyst of vanadium (V) oxide is used. In a particular equilibrium mixture at 400 C the partial pressures of sulphur dioxide and of oxygen were 0.100 atm and 0.500 atm respectively. Show that the yield of SO3 is about 95% of the equilibrium mixture. (5)

(b) Explain what is meant by dynamic equilibrium. (1)-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------(c) State the effect on the value of Kp for this equilibrium of the following.(i) Increasing the total pressure. (1)

---------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------(ii) Increasing the temperature. (1)

---------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------(iii) Adding a catalyst. (1)

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(iv) In the table below state the effect on this reaction of increasing the temperature and of increasing the pressure. (2) Effect on the rate of thereactionEffect on the position ofequilibrium

Increasing thetemperature

Increasing the pressure

(v) Use your answer to (c)(ii) & (iv) , explain the effect t of increase in temperature of the yield of this process (2)(2)---------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------(d) Sulphuric acid dissociates in water according to the equations:H2SO4 + H2O H3O+ + HSO Step 1HSO+ H2O H3O+ + SO Step 2The dissociation constant for the first dissociation is very large ; that for the second is 0.01 mol dm3 at 25 C.(i) Identify the Bronsted Lowry acid/base conjugate pairs in stage 1 of its dissociation Stage 1: (1) Acid 1 -------------------------------------------------------- Base 1 ---------------------------------------------------------- Acid 2 -------------------------------------------------------- Base 2 ----------------------------------------------------------

(ii) On the basis of the behaviour of HSO4 in both of the above equations prove that conjugate is a relative term and links a specific pair of acids and bases (2)---------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------(iii) Explain why only a very little dissociation occur in step 2 of its dissociation . (1)------------------------------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------------------------ (ii) Calculate the pH of an aqueous solution containing 0.200 mol dm3 hydrogen ions. (1)

(ii) The pH of 0.100 mol dm3 sulphuric acid is 0.98. Explain why this is so close to the pH of 0.100 mol dm3 HCl which is 1.0. (2)

---------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (Total for Question 17 = 20marks)

18. Asparagine is a vital component of many plants, where it is used to transport and store nitrogen. It has the structure shown below.

(a) State the three functional groups present in asparagines. (3)

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(b) Asparagine occurs as two stereoisomers. Name the type of stereoisomerism and explain why it occurs in this particular molecule. (2)

Type of isomerism:---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- Explanation : ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------

(c) Draw the structure of the organic product formed when asparagine reacts with

(i) NaOH. (2)

(d) When cooking food at high temperature, asparagine can react to produce2-propenamide (acrylamide), also a white solid and a possible carcinogen.

2-propenamide

(i) Give one test, including reagents and expected observations, which would distinguish between the two white solids asparagine and 2-propenamide. (2)

Test:-

---------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------

Observation:-

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(ii) One method which has been suggested to remove 2-propenamide from food is to induce alkene polymerisation.

Classify the type of reaction involved in alkene polymerisation. (1)

---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- Draw the repeating unit for the polymer formed by the alkene polymerisation of 2-propenamide. (1)

(Total for Question 18 = 11 marks) (Total for section B= 51 Marks)SECTION C(e) In moths a pheromone, P, acts as an attractant for the opposite sex. P has the molecular formula C7H12O.What can be deduced about the structure of P from the following information?(a)(i) 1 mole of P reacts with 1 mole of Br2 molecules to form a compound with the formula C7H12OBr2. (1) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (ii) What will you observe when the reaction (a)(i) occurred (1)---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (iii) Compound Q does not react with sodium. (1)---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (ii) When lithium tetrahydridoaluminate is reacted with P a compound with the formula C7H14O is formed (1)---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (iii) P forms an orange precipitate with 2,4-dinitrophenylhydrazine. (1) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (iv) When P is heated with Fehlings or Benedicts solution, the solution remains blue. (1) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (v) When warm with Iodine & sodium hydroxide solution , no yellow solid with an antiseptic smell (1)---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (v) P is a Z-isomer. (1)

(b)What does the following physical data tell you about the structure of P? Use your Data booklet where necessary.(i) The infrared spectrum of P has the following absorptions at wave numbers above 1600 cm1. Identify the stretching absorptions listed belowA medium stretching absorption at 3060 cm1 (1) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------A medium stretching absorption at 2920 cm1 (1)---------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------A strong stretching absorption at 1690 cm1 (1) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (ii)The nmr spectrum does not have a peak corresponding to a chemical shift, ppm, of between 9 and 10. (1)

---------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (iii) The mass spectrum showed the presence of peaks at mass/charge ratios of 15 and 29, but no peak at 43. (3)---------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------(e) Given that P has a straight chain of carbon atoms in its formula, use the information you have deduced above to suggest a displayed formula for the pheromone P. (2)

(f) How could you use a purified sample of the orange precipitate in (a)(iii) to confirm the formula of P? (2)---------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- (Total for Question 15= 19 marks) (Total for section C = 19 Marks)

AHS/Dept of Science / Semester- 4(April 2012)/ Grade 12/ Chemistry - Unit 4 17 of 17