
	Trending ▼ ICSE CBSE 10th ISC CBSE 12th CTET GATE UGC NET Vestibulares ResFinder

GCE MAY 2008 : (A2 3A) Synoptic Paper

16 pages, 45 questions, 0 questions with responses, 0 total responses,

	gce	+Fave Message
	Profile Timeline Uploads Q & A

Home > gce >

Instantly get Model Answers to questions on this ResPaper. Try now!
NEW ResPaper Exclusive!

Formatting page ...

Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2008 Chemistry assessing Module 6A: Synoptic Paper A2C31 Assessment Unit A2 3A [A2C31] FRIDAY 30 MAY, 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 five questions. Section A contains a Planning Exercise. Section B contains four questions assessing different aspects of the specification. INFORMATION FOR CANDIDATES The total mark for this paper is 80. Quality of written communication will be assessed in question 1. Figures in brackets printed down the right-hand side of pages indicate the mark awarded to each question or part question. A Periodic Table of Elements (including some data) is provided. For Examiner s use only Question Number 1 2 3 4 5 Total Marks A2C3AS8R 3831.02 Marks Section A Examiner Only Marks 1 Remark Planning Exercise Preparation of carbon tetrabromide (tetrabromomethane) by the reaction of propanone with bromine. CH3COCH3 + 5OH + 4Br2 CBr4 + CH3CO2 + 4Br + 4H2O Dissolve 3 cm3 of bromine (density = 3.10 g cm 3) in 60 cm3 of 1M sodium hydroxide solution with stirring. Add 10 cm3 of water to 0.5 cm3 of propanone (density = 0.79 g cm 3). Add the solution produced, drop by drop, to the solution of bromine in sodium hydroxide shaking the mixture vigorously after each addition. After considerable shaking solid carbon tetrabromide is formed. Filter using Buchner (vacuum) filtration. Wash the solid with water to remove bromide ions and recrystallise from methanol. Pure carbon tetrabromide has a melting point of 88 90 C and boils at 190 192 C. (a) State and explain the safety precaution, other than the use of eye protection, that should be carried out during this preparation. _________________________________________________________ _______________________________________________________ [2] (b) (i) Explain why stirring or shaking is not required in making a solution of propanone in water. ______________________________________________________ ____________________________________ ________________ [1] (ii) Suggest why the solution of propanone in water is added drop by drop. ______________________________________________________ ____________________________________ ________________ [1] A2C3AS8R 3831.02 2 [Turn over (c) (i) Calculate the moles of propanone, bromine (Br2) and sodium hydroxide which are being used. Examiner Only Marks Remark ______________________________________________________ ______________________________________________________ ______________________________________________________ ____________________________________ ________________ [3] (ii) Deduce which reagents are in excess. ____________________________________ ________________ [1] (iii) Calculate the percentage yield if the mass of carbon tetrabromide obtained is 1.7 g ______________________________________________________ ______________________________________________________ ____________________________________ ________________ [2] (d) Explain, using a diagram, how vacuum filtration is carried out. _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] A2C3AS8R 3831.02 3 [Turn over (e) How could you show that the filtered solid is free of bromide ions? Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (f) State two ways by which you could judge the purity of the carbon tetrabromide obtained and state what you would expect for an impure sample. _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] Quality of written communication (based on the whole of the question) [2] A2C3AS8R 3831.02 4 [Turn over BLANK PAGE (Section B starts on the next page) A2C3AS8R 3831.02 5 [Turn over Section B Examiner Only Marks Remark Answer all four questions 2 Toluidine red may be synthesised using the following scheme. CH3 CH3 Step 1 CH3 CH3 Step 2 Step 3 NO2 NO2 NH2 NHCOCH3 NHCOCH3 Step 4 H+ CH3 OH N=N CH3 CH3 Step 6 Step 5 NO2 O2N + N2 Cl NO2 NH2 (a) (i) Name the reagents used in the following steps Step 1 ____________________________________________ [1] __ Step 2 ____________________________________________ [1] __ Step 3 ____________________________________________ [1] __ Step 5 ____________________________________________ [1] __ (ii) Draw the structure of the reagent in step 6. [1] (b) State and explain the conditions needed for step 5. _________________________________________________________ _______________________________________________________ [2] A2C3AS8R 3831.02 6 [Turn over (c) Explain, using chemical principles, why toluidine red is coloured. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (d) The melting point of toluidine red is 270 272 C. Suggest, using three types of intermolecular forces, why it has such a high melting point. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] A2C3AS8R 3831.02 7 [Turn over 3 Succinic acid was originally obtained by the distillation of amber (Latin: succinum, amber). It is a solid with a melting point of 185 186 C. Examiner Only Marks Remark CH2COOH | CH2COOH Succinic acid (a) Suggest a systematic name for succinic acid. _______________________________________________________ [2] (b) The nmr spectrum of succinic acid is shown below. 6 5 4 3 2 1 0 (i) The signal at 0 is due to TMS. Give the name and formula of TMS. ____________________________________ ________________ [2] (ii) Use the integration curve to identify and explain which hydrogen atoms are responsible for the signals at 4.9 and 2.8. ______________________________________________________ ____________________________________ ________________ [2] (iii) Explain why the signal at 4.9 is at a lower chemical shift than the one at 2.8. ______________________________________________________ ____________________________________ ________________ [2] (iv) Explain why no spin spin splitting occurs. ______________________________________________________ ____________________________________ ________________ [2] A2C3AS8R 3831.02 8 [Turn over (c) The mass spectrum of succinic acid is shown below. Examiner Only Marks Remark 100 80 60 relative abundance 40 20 0.0 0.0 40 80 120 m/z (i) What name is given to the peak at 55 which is the highest peak in the spectrum? ____________________________________ ________________ [1] (ii) Deduce the ions responsible for the peaks at 73 and 100. ____________________________________ ________________ [1] ____________________________________ ________________ [1] A2C3AS8R 3831.02 9 [Turn over (d) Succinic acid is converted into a dimethyl ester when reacted with methanol in the presence of concentrated sulphuric acid. The ester is a liquid with a boiling point of 196 200 C. Examiner Only Marks Remark (i) Write the equation for the reaction. ____________________________________ ________________ [2] (ii) Explain the role of sulphuric acid in the reaction. ______________________________________________________ ____________________________________ ________________ [1] (iii) Suggest why the use of a liquid rather than a solid is more advantageous in carrying out analysis by GLC. ______________________________________________________ ____________________________________ ________________ [1] (e) Succinic acid is a weak diprotic acid with pKa values of 4.2 and 5.6. (i) Suggest the meaning of the term diprotic acid. ______________________________________________________ ____________________________________ ________________ [1] (ii) Using the lower pKa value only, calculate the pH of a 0.1 M solution of succinic acid. ______________________________________________________ ______________________________________________________ ______________________________________________________ ____________________________________ ________________ [3] A2C3AS8R 3831.02 10 [Turn over 4 Warfarin has been used to destroy rodents. It acts by preventing the clotting of blood in a mechanism involving vitamin K. It has been replaced as a rodenticide by better anticoagulants, but it has now found a major use in treating human heart disease. The formula is shown below. Examiner Only Marks Remark O O C O C C CH CH2 C CH3 OH (a) What is the molecular formula for Warfarin? _______________________________________________________ [1] (b) Warfarin is a chiral molecule. (i) Explain the term chiral. ______________________________________________________ ____________________________________ ________________ [1] (ii) Circle the chiral centre in Warfarin. [1] (iii) The two chiral isomers of Warfarin display different biological activity. Using a mechanism of enzyme activity, suggest why the activities differ. ______________________________________________________ ____________________________________ ________________ [2] A2C3AS8R 3831.02 11 [Turn over (c) Warfarin is a crystalline solid, melting point 159 161 C. The identity of Warfarin may be confirmed by measuring the melting point of its 2,4-dinitrophenylhydrazone. Examiner Only Marks Remark (i) What functional group does Warfarin contain which would cause it to react with 2,4-dinitrophenylhydrazine? ____________________________________ ________________ [1] (ii) Write a structural equation for the reaction of the appropriate functional group in Warfarin with 2,4-dinitrophenylhydrazine (there is no need to draw the structure of the complete Warfarin molecule). ____________________________________ ________________ [3] (d) Warfarin reacts with phosphorus pentachloride. (i) Which functional group in the Warfarin molecule reacts with phosphorus pentachloride? ____________________________________ ________________ [1] (ii) Name the gas given off from this reaction and describe a positive test for this gas. ______________________________________________________ ____________________________________ ________________ [2] A2C3AS8R 3831.02 12 [Turn over 5 Sodium cobaltinitrite, Na3[Co(NO2)6], is a reagent that has been used to test for potassium ions in solution. It is a yellow crystalline solid and may be precipitated from aqueous solution by the addition of ethanol. Examiner Only Marks Remark (a) Calculate the percentage of cobalt in sodium cobaltinitrite. _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (b) Sodium cobaltinitrite can be prepared by drawing a current of air through a warm solution containing cobalt(II) nitrate, sodium nitrite and ethanoic acid. Co2+ + NO2 + 2H+ Co3+ + NO + H2O Co3+ + 6NO2 [Co(NO2)6]3 (i) Explain the role of the ethanoic acid. ____________________________________ ________________ [1] (ii) Using oxidation numbers, explain any redox reactions taking place. ______________________________________________________ ______________________________________________________ ____________________________________ ________________ [3] (iii) State the expected overall colour change. ____________________________________ ________________ [1] A2C3AS8R 3831.02 13 [Turn over (c) The cobaltinitrite ion has a similar structure to the [Co(NH3)6]3+ ion. Examiner Only Marks Remark (i) Name the shape of the cobaltinitrite ion. ____________________________________ ________________ [1] (ii) Draw the structure of the cobaltinitrite ion. [1] (d) When sodium cobaltinitrite is added to a solution containing potassium ions, a precipitate is obtained. The reaction can be used as a qualitative test for potassium. (i) Deduce the formula of potassium cobaltinitrite. ____________________________________ ________________ [1] (ii) Potassium ions can also be detected by flame spectroscopy. Explain how this is done and the result expected. ______________________________________________________ ______________________________________________________ ____________________________________ ________________ [3] THIS IS THE END OF THE QUESTION PAPER A2C3AS8R 3831.02 14 [Turn over A2C3AS8 3831 15 S 8/07 1298-001-1

Formatting page ...

Additional Info : Gce Chemistry May 2008 Assessment Unit A2 3A Module 6A: Synoptic Paper
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

gce chat

Horizontal lines at:
Guest Horizontal lines at:
AutoRM Data:
Box geometries: