DHS Prelim P2

CANDIDAT E NAME ____________________________ CG________ DUNMAN HIGH SCHOOL (SENIOR HIGH) YEAR 6 PRELIMINARY EXAMINATION 2009 H1 CHEMISTRY Paper 2 8872/02 22 September 2009 2 hours Additional materials: Answer Paper Data Booklet INSTRUCTIONS TO CANDIDATES 1 Write your name and class on all the work you hand in. 2 Write in dark blue or black pen on both sides of the paper. 3 You may use a soft pencil for any diagrams, graph or rough working. 4 The number of marks is given in brackets [ ] at the end of each question or part question. 5 You may use a calculator. 6 At the end of the exami nation, fasten all your work securely together. Section A FOR EXAMINER’S USE Question Marks 1 /6 2 /8 3 /11 4 /15 Paper 2 Section A /40 5 /20 6 /20 7 /20 Paper 2 Section B /40 Paper 1 /30 Total /110 Grade Answer all questions. Section B Answer tw o questions on separate answer paper. This document consists of 13 printed pages and 1 blank page. [Turn over

2 Section A Answer all the questions in this section in the spaces provided. [Turn over 1 Antimony (Sb), with atom ic number 51 has been known since about 4000BC. Nowadays, its main use is to harden and to strengthen lead alloys. A typical sample of antimony consists of two isotopes and has the following composition by mass: 121Sb, 57.25%, 123Sb, 42.75%. (a) (i) Calculate the relative atomic mass of the antimony sample. (ii) Define the term relative atomic mass. [3] Antimony is produced in two–stage process from the sulphide ore, Sb2S3. The ore is first roasted in oxygen to form the oxide. 2Sb2S3(s) + 9O2(g)  Sb4O6(s) + 6SO2(g) The oxide is then reduced with carbon. Sb4O6(s) + 3C(s)  4Sb(s) + 3CO2(g) (b) Showing your working clearly, calculat e the volume of ca rbon dioxide that would be produced by the processing of 3400 g of Sb 2S3. [Assume that 1 mole of gas occupies 24 dm3 under experimental conditions.] [3] [Total: 6]

3 2 The figure shows a plot of first i onisation energy against atomic number for the elements of atomic number 10 to 18. (The letters are not the chemical symbols for the elements concerned.) (a) Write an equation to define the first ionisation energy of A. [1] (b) Describe the general trend of the ionisation energies from B to I as shown in the graph above. [2] (c) Explain briefly why the first ionisation energy of D is less than C. [2] A First ionisation energy / kJ mol–1 I F H C G E D B Atomic number [Turn over

4 (d) Draw the shape of the orbital from which electron is lost when (i) Element B forms a singly charged ion, (ii) Element H forms a singly charged ion. [2] (e) Give the full electronic configuration of the element labeled F. [1] [Total:8] 3 Each of these elem ents in Period 3 will react with oxygen given suitable conditions. Period 3 Na Mg Al Si P S Cl (a) Which element(s) can exist (i) as diatomic molecules at room temperature, ( i i ) as macromolecular structures? [2] [Turn over

5 (b) Two elements form chlorides with formulae of the type XC l3. Draw the dot– and–cross diagram for these two chlori des, state the shapes and suggest values for the bond angles. [4] (c) (i) One element form chloride of the type YC l 2 which reacts with water to give a slightly acidic solution. Name t he element, and account for the pH value of YCl2 in water. Write a balanced equation to illustrate your answer. (ii) One element forms a chloride of the type ZC l 4, which reacts with water to give a strongly acidic solution. Na me the element a nd write a balanced equation for the chloride reacting with water. [5] [Total: 11] [Turn over

6 4 Oseltamivir (Tamiflu) is an antiviral drug th at slows the spread of non–resistant strains of the influenza virus between cells in the body. It blocks the action of a viral enzyme called neuraminidase and has si nce been indicated for the treatment of H5N1 and H1N1 infection. The st andard adult dosage is 75 mg twice daily. Compound Z is a derivative of oseltamivir t hat maybe investigated for antiviral activities. ON H2 OOC H 3 C1 CH3 CH3 ON H CH3 oseltamivir Mr : 312.4 OH OOC 3 OC H 3 H Z (a) (i) A male adult patient has been put on a 5–day oseltamivir treatment. Calculate the total number of moles of oseltamivir taken by this patient over this period of treatment. (ii) Describe the hybridisation, geometry and bond angle about C 1 atom. [4] (b) (i) Name the functional groups present in Compound Z. [Turn over

7 (ii) Compound X can be synthesised from Z using 2 consecutive reactions. Give the reagents and conditions for both reactions. Name the type o f reactions involved. OH OOC 3 OHC H 3 OH OH H X Step I: Reagent: Condition: Type of reaction: Step II: Reagent: Condition: Type of reaction: [5] (c) (i) Draw the products formed when Compound Z is reacted with dilute HC l under reflux. [Turn over

8 (ii) Describe a chemical test to di stinguish the products from (c)(i). State the observations with each compound an d write balanced equation(s) for reaction(s) involved. [6] [Total:15] [Turn over

9 C Section B Answer tw o questions from this section on separate answer paper. 5 (a) A monobasic acid HA, extracted from a fruit has a pH of 3.5 (i) Calculate the concentration, in mol dm-3, of hydrogen ions in the acid HA. (ii) 25.0 cm 3 of a sample of the acid HA was titrated with 0.25 mol dm –3 aqueous NaOH. 21.25 cm 3 of the aqueous NaOH was required to reach equivalence point. Calculate the concentration, in mol dm -3, of the acid HA. (iii) Based on your answers to (a)(i) and (a)(ii) above, what can you deduce about the strength of the acid HA? Give a reason for your deduction. (iv) Suggest a suitable indicator for the above titration. [5] (b) Propanoic acid is a weak acid that undergoes esterification with ethanol to form the ester, ethylpropanoate. H 3CH2COOH(l) + CH3CH2OH(l) CH3CH2COOCH2CH3(l) + H2O(l) The graph below shows the change in num ber of moles of the reactants and products in the reaction mixture. The changes in the number of moles of CH 3CH2COOCH3CH2 and H2O with time are the same. 0.12 0.10 0.08 0.00 0.02 0.04 0.06 0 1 2 3 4 5 6 7 8 Time / min No. of mol C C COOC CH2O CH3CH2COOH CH3CH2OH [Turn over

10 (i) Write an expression to define Kc for the equilibrium. (ii) State the time at which equilibrium is established. (iii) Calculate the value of Kc. (iv) Given that the forward reaction is exothermic, state and explain the effect on the yield of the ester and the value of K c, when the temperature is increased. [6] (c) A mixture of propanoic acid and its salt, sodium propanoate, is o ften used in food products as a buffer to regulate the acidity of the products. (i) Explain what is meant by a buffer solution. (ii) Explain, using suitable equations, how a solution of propanoic acid and sodium propanoate acts as a buffer system. [4] (d) (i) Identify and draw the types of structural isomerism that ethyl propanoate can exhibit. (ii) Describe a chemical test to distinguish between the two isomers in (d)(i). Give the reagents and conditions for the test, and describe the observation for each compou