Centre Number 71 Candidate Number ADVANCED General Certificate of Education January 2007 Chemistry Assessment Unit A2 1 assessing Module 4: Further Organic, Physical and Inorganic Chemistry A2C11 [A2C11] THURSDAY 11 JANUARY, MORNING TIME 1 hour 30 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Answer all sixteen questions. Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering. Answer all six questions in Section B. Write your answers in the spaces provided in this question paper. INFORMATION FOR CANDIDATES The total mark for this paper is 90. Quality of written communication will be assessed in question 15(c)(i). In Section A all questions carry equal marks, i.e. two marks for each question. In Section B the figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. A Periodic Table of Elements (including some data) is provided. A2C1W7 2738 For Examiner s use only Question Number Section A 1 10 Section B 11 12 13 14 15 16 Total
Section A For each of the questions only one of the lettered responses (A D) is correct. Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet. 1 Which one of the following alcohols does not undergo oxidation when treated with warm acidified potassium dichromate(vi)? A B C D 3-methylpentan-1-ol 3-methylpentan-2-ol 2-methylpentan-2-ol 2-methylpentan-1-ol 2 Toothpaste for sensitive teeth contains 10% by mass of hydrated strontium chloride, SrCl 2.6H 2 O. What is the mass of strontium contained in 100 g of toothpaste? A B C D 1.8 g 3.3 g 3.8 g 4.6 g 3 Which one of the following does not contain an asymmetric centre? A CH 3 CH(CH 3 )CH 2 CH 3 B CH 3 CH(OH)CH 2 CH 3 C CH 3 CHClCH 2 CH 3 D CH 3 CH(NH 2 )CH 2 CH 3 A2C1W7 2738 2 [Turn over
4 Chlorine reacts with water according to the equation below. Cl 2 + H 2 O HOCl + H + + Cl Which one of the following substances when added would move the equilibrium to the right? A B C D hydrogen hydrogen chloride sodium chloride sodium hydroxide 5 The concentration of hydrogen ions in a solution is 1 10 6 mol dm 3. What is the concentration of hydroxide ions in the solution? A 1 10 4 mol dm 3 B 1 10 7 mol dm 3 C 1 10 8 mol dm 3 D 1 10 14 mol dm 3 6 The kinetics of the reaction of nitrogen(ii) oxide with hydrogen were investigated. The following data were obtained. 2NO + 2H 2 2H 2 O + N 2 [NO] mol dm 3 1.0 3.0 3.0 [H 2 ] mol dm 3 1.0 1.0 2.0 Relative rate of reaction 1 9 18 What is the rate equation for the reaction? A rate = k[no][h 2 ] B rate = k[no] 2 [H 2 ] C rate = k[no] 2 [H 2 ] 2 D rate = k[no][h 2 ] 2 A2C1W7 2738 3 [Turn over
7 Which one of the following is used for the rate constant of a third order reaction? A s 1 B mol dm 3 s 1 C mol 2 dm 6 s 1 D mol 2 dm 6 s 1 8 For which one of the following titrations is there no suitable indicator? A B C D Na 2 CO 3 (aq) against H 2 SO 4 (aq) NH 3 (aq) against CH 3 COOH(aq) Ca(OH) 2 (aq) against HCl(aq) I 2 (aq) against Na 2 S 2 O 3 (aq) 9 The conjugate base of methanol is A OH B CH 3 O C CH 3 + D CH 3 O + 10 For which one of the following chlorides is it not possible to construct a Born-Haber cycle? A B C AgCl HCl RbCl D MgCl 2 A2C1W7 2738 4 [Turn over
BLANK PAGE (Section B starts overleaf) A2C1W7 2738 5 [Turn over
Section B Answer all six questions in the spaces provided. 11 When chlorine gas is passed into aqueous sodium thiosulphate the products are sulphate(vi) ions, chloride ions, hydrogen ions and Na 2 S 2 O 3. (a) Write a balanced ionic equation for the reaction. [2] (b) State the change in oxidation numbers for chlorine and sulphur in this reaction. [2] (c) State the industrial use of the reaction between chlorine and sodium thiosulphate. [1] A2C1W7 2738 6 [Turn over
12 The diagram shows how to distinguish between propanal and propanone. Tollen s reagent + propanal or propanone water heat (a) State the metal ion present in Tollen s reagent. [1] (b) State the functional group present in both propanal and propanone. [1] (c) Explain why hot water is used. [1] (d) State what is observed in separate experiments with propanal and propanone. Propanal [1] Propanone [1] A2C1W7 2738 7 [Turn over
13 Poisonous carbon monoxide may be detected and estimated by several methods. (a) A sample of gas is believed to be pure carbon monoxide. How could you prove, using combustion, that the gas is carbon monoxide? [2] (b) Carbon monoxide can be detected using a piece of filter paper soaked in palladium chloride. The paper blackens due to the formation of palladium by a redox reaction. CO + PdCl 2 + H 2 O CO 2 + 2HCl + Pd (i) Explain the meaning of the term redox. (ii) Calculate the number of milligrams of palladium formed if 360 dm 3 of air containing 0.001% by volume of carbon monoxide are in contact with a piece of filter paper containing palladium chloride. Assume the reaction takes place at 20 C and a pressure of one atmosphere and the palladium chloride is in excess. [3] A2C1W7 2738 8 [Turn over
(c) The traditional quantitative method of analysis is to pass air containing carbon monoxide over iodine pentoxide. Any carbon dioxide present in the air is removed beforehand. 5CO(g) + I 2 O 5 (s) 5CO 2 (g) + I 2 (s) The carbon dioxide formed is passed through baryta water (barium hydroxide solution) to form a precipitate of barium carbonate, BaCO 3, which is filtered, washed and weighed. (i) Draw a diagram of the labelled apparatus which could be used to pass air over iodine pentoxide and then immediately pass the air through baryta water. [2] (ii) Write the equation for the reaction of barium hydroxide with carbon dioxide. (iii) Calculate the percentage of carbon monoxide, by volume, in 30 dm 3 of air if 0.493 g of barium carbonate are formed. [3] A2C1W7 2738 9 [Turn over
(d) Electrochemical methods may be used to detect carbon monoxide. The reactions occurring in one detector are: At the positive electrode CO + H 2 O CO 2 + 2H + + 2e E = 0.10 V At the negative electrode O 2 + 4H + + 4e 2H 2 O E = +1.23 V (i) Write the overall redox equation for the cell. (ii) Calculate the emf of the cell formed. A2C1W7 2738 10 [Turn over
14 Fats are naturally occurring esters of long chain fatty acids and glycerol. The fatty acids may be saturated or unsaturated. (a) Fats may be produced by the equilibrium reaction between a fatty acid and glycerol. CH 2 OH CH 2 O.OCR CHOH + 3RCOOH CHO.OCR + 3H 2 O CH 2 OH CH 2 O.OCR (i) Name a catalyst that can be used in this reaction. (ii) State the systematic name for glycerol. [2] (iii) The fat may alternatively be produced by the reaction of an acyl chloride with glycerol. Write the equation for the reaction and explain why an equilibrium is not produced. [2] A2C1W7 2738 11 [Turn over
(b) The most important unsaturated fatty acids have 18 carbon atoms with one or more double bonds. Oleic acid contains one double bond and linolenic acid contains three. (i) Draw the structure of cis oleic acid. [1] (ii) In linolenic acid, CH 3 CH 2 CHCHCH 2 CHCHCH 2 CHCH(CH 2 ) 7 COOH, each double bond has a cis structure. Draw the structure of the acid. [1] (iii) Write the formula of stearic acid which is saturated and also contains 18 carbon atoms. A2C1W7 2738 12 [Turn over
(c) (i) A comparison between the degree of unsaturation of oils and fats can be made using bromine water. Samples of lard and olive oil can be dissolved in a solvent and treated with bromine water. Explain how you would carry this out naming an appropriate solvent and state the results expected. [3] Quality of written communication [2] (ii) The degree of unsaturation of a fat or oil may be measured using the iodine value. Define the term iodine value. [2] (iii) Triolein has a relative molecular mass of 884 and one molecule contains three double bonds. Using your definition calculate the iodine value of triolein. [3] A2C1W7 2738 13 [Turn over
15 Chlorination of ethanoic acid produces three substituted chloroethanoic acids. The first step is: Cl 2 + CH 3 COOH CH 2 ClCOOH + HCl Data on the acids is shown below. Acid Boiling pka Dissociation LD 50 of point/ C constant/ sodium salt mol dm 3 Monochloroethanoic acid 189 2.82 1.5 10 3 0.5 Dichloroethanoic acid 194 5.1 10 2 2.8 Trichloroethanoic acid 196 0.70 2.0 10 1 3.3 (a) (i) Suggest why all three acids have a greater boiling point than that of ethanoic acid which is 118 C. [2] (ii) Calculate the pka of dichloroethanoic acid. (b) Trichloroethanoic acid is almost as strong as mineral acids such as hydrochloric acid. Calculate the ph of a 0.1 mol dm 3 solution of trichloroethanoic acid. [3] A2C1W7 2738 14 [Turn over
(c) The sodium salt of monochloroethanoic acid together with monochloroethanoic acid can act as a buffer solution. (i) Explain the term buffer. [2] (ii) Use equations to explain how this buffer mixture is able to remove both H + and OH ions if an acid or alkali is added. [2] (iii) Explain why a mixture of sulphuric acid and sodium sulphate cannot act as a buffer. (d) The LD 50 is an indication of the poisonous nature of a compound. It is the number of milligrams per kg of body mass that will kill a person. Calculate the number of moles of sodium monochloroethanoate that will kill a man weighing 90 kg. [3] A2C1W7 2738 15 [Turn over
16 Aluminium dissolves slowly in cold dilute hydrochloric acid but rapidly in hot concentrated hydrochloric acid. Dilute sulphuric acid has little effect but hot concentrated sulphuric acid dissolves the aluminium in a similar way to copper. (a) The aqueous solution of aluminium in hydrochloric acid deposits crystals of Al 2 Cl 6.12H 2 O. On heating, the hydrate decomposes, giving off fumes of hydrogen chloride and leaving aluminium oxide. (i) Write the equation for the decomposition of the hydrate. (ii) Explain how you could confirm that hydrogen chloride was given off. [2] (b) Aluminium chloride can also be obtained by passing dry chlorine over aluminium metal. (i) Write the equation for the formation of aluminium chloride. (ii) Explain why the chlorine must be dry. (iii) Aluminium chloride is believed to exist as a dimeric structure. Complete the diagram below; show the outer electrons and draw the two coordinate bonds, which hold the AlCl 3 molecules together. Cl Cl Cl Al Al Cl Cl Cl (iv) State one property, which shows that aluminium chloride is covalent rather than ionic. [3] A2C1W7 2738 16 [Turn over
(c) Aluminium sulphate is formed when either aluminium oxide or aluminium is dissolved in sulphuric acid. (i) Write the equation for the reaction of aluminium with hot, concentrated sulphuric acid. (ii) Aluminium oxide also dissolves in alkalis. Write the equation for its reaction with sodium hydroxide and state the name given to an oxide, which dissolves in acids and alkalis. [2] (iii) Explain why a solution of aluminium sulphate is acidic. [2] THIS IS THE END OF THE QUESTION PAPER A2C1W7 2738 17 [Turn over
S 6/06 2300 9-046-1 [Turn over