Basic chemistry test 2011 and answers

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Basic chemistry test 2011 and answers

  1. 1. 1. Diagram 1 shows the symbol of the atoms of element X , element Y and element Z . The letters used are not the actual symbols of the elements. 23 16 35 X Y Z 11 8 17 Diagram 1 a) State the proton number of the atom of element X _________________________________________________________________________ [1 mark] b) Which element is a halogen? Explain ..................................................................................................................................................... [2 mark] c) i) Identify the position of element Y in Periodic Table of Elements _______________________________________________________________________ [1 mark] ii) Explain why element Y is placed at the position identified in d(i)
  2. 2. _______________________________________________________________________ [1 mark]d) i) Write the formula of the compound formed between element X and Y _______________________________________________________________________ [1 mark] ii) State two physical properties of the compound formed in e(i) _______________________________________________________________________ _______________________________________________________________________ [2 marks] iii) Draw the electron arrangement of the compound formed in e(i) [2 marks]
  3. 3. 2. Diagram 2 shows the apparatus set up for two types of cells, P and Q Diagram 2 a) State one difference in energy change between cell P and cell Q In cell P energy change is from ....................................................to .............................. In cell Q energy change is from ....................................................to .............................. [1 mark] b) What is the product at the anode in cell P? ___________________________________________________________________________ [1 mark] c) Write the half equation for the discharge of cation in cell P __________________________________________________________________________ [1 mark] d) State one observation at electrode zinc in cell Q __________________________________________________________________________ [1 mark]
  4. 4. e) Diagram 2.2 shows the apparatus set-up for the electrolysis of sodium chloride solution using carbon electrodes i) State all ions attracted towards electrode P and Q Electrode P Electrode Q [2 marks] ii) State which ion discharge at electrode Q. Explain why _______________________________________________________________________ _______________________________________________________________________ [2 marks] iii) Describe one chemical test to identify gas X _______________________________________________________________________ _______________________________________________________________________ [2 marks] Total mark =10m
  5. 5. 3) Diagram 3 shows a series of reaction of compound P. Compound P and compound Q are shownin condensed structural formulae. Compound Q CO2 + H2O CH3CH2 CH3 Combustion I II Compound P Compound R CH2=CHCH3 Steam and Phosphoric acid III + Ethanoic acid + concentrated sulphuric acid Compound S Diagram 3
  6. 6. (a) Compound P is propene . State the homologous series of compound P _________________________________________________________________ [1 mark](b) Compound Q is used as a cooking gas. i) State the molecular formula of compound Q ....................................................... [ 1 mark] ii) Write a chemical equation for the combustion of compound Q to produce carbon dioxide and water ___________________________________________________________________ [2 mark](c) Compound P can be changed to compound R which is an alcohol through process II. Name process II ............................................................................................ [ 1mark] State the general formula for alcohol _____________________________________[1 mark](d) Explain briefly how compound S can be prepared from compound R in laboratory. In your answer include the appropriate reagents and condition for the preparation. __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ [3 marks](e) An organic compound W has a molecular formula of C4 H8 . Compound W has 3 isomers. Draw two structural formulae of two isomers of W
  7. 7. [2 marks] Total mark= 11m Max mark=10m 4) Natural rubber is a polymer, where the monomer is isoprene or 2- methylbuta-1,3-diene. Natural rubber is obtained from latex, which is a colloid made up of rubber particlesand water. a) Draw i) Structural formula of isoprene (1m) ………………………………………………………………………… labelled diagram of latex particle in water (2m) …………………………………………………………………………
  8. 8. b) Explain why latex in the original form does not coagulate (2m) ……………………………………………………………………....................………………… ……………………………………………………………………………......................………… c) However, or when latex is exposed to air, coagulation of latex occur. Explain (3m) …………………………………………………………………………….............................…………… …………………………………………………………………………….........................…………… ………………………………………………………………………………...............................………… d) The properties of natural rubber can be improved by treating it with sulphur. i) Name this process (1m) ………………………………………………………………………… ii) State ONE use of the treated rubber above (1m) ……………………………………………………………………… Total= 10m5.
  9. 9. Potassium sulphate solution Barium Chloride solution Diagram 5Diagram 5 above show the experiment to determine the heat of precipitation of bariumsulphate. 50 cm3 of 1.0 mol dm-3 potassium sulphate solution and 50 cm3 of 1.0 mol dm-3 bariumchloride solution are poured into two separate polystyrene cups. Then both solution are added.The results are shown as below Initial temperature of potassium sulphate = 29.5 oC Initial temperature of barium chloride = 29.5oC Maximum temperature of mixture = 34.50C a) What is meant by the heat of precipitation of barium sulphate? [1 mark] b) Write an ionic equation for the reaction _______________________________________________________________ [1 mark]
  10. 10. c) State one observation for the experiment [1 mark]d) Calculate i. The heat released in the experiment [Specific heat capacity of water = 4.2 Jg-1oC-1, Density of water = 1.0 g cm-3] [2 mark] ii. The number of moles of barium sulphate formed [1 marks] iii. The heat of precipitation of barium sulphate
  11. 11. No. Answers Mark1. a) 11 1b) Z 1 Because the valence electron Is 7 1c)i) Group 16, Period 2 1ii) It has 2 shells occupied with electrons and the valence 1 electron is 6d)i) X2Y 1d)ii) -soluble in water 2 -insoluble in organic solvent -can conduct electricity in aqueous and molten state -high melting and boiling pointd)iii) 2 -Correct no of shells -correct no. of electron on each shell and charge [2 marks] e) Draw the energy level diagram for the precipitation of barium sulphate [2 marks] Total =10m -----END OF QUESTIONS-----Standardised test form 5 –sem1 – 2011 chemistry = suggested answers
  12. 12. No. Answers Mark2. a Cell P: Electrical energy  Chemical energy 1 ) Cell Q: Chemical energy  Electrical energyb) Oxygen and water 1c) Cu2+ + 2e  Cu 1d) Zinc electrode becomes thinner 1e)i) 2 Electrode P Electrode Q H+ , Na + Cl - , OH -ii) Chloride ion because the concentration of chloride ion is 2 higher than hydroxide ioniii) Put the burning/lighted wooden splinter into the test tube, a 2 ‘pop’ sound producedScheme answer no 3 Questio Suggested Answer marks n 3 a. Alkene 1m b .i C3H8 1m ii C3H8 + 5O2  3 CO2 + 4 H2O 2m c. i Hydration 1m ii Cn H2n +1 OH n=1,2,3…… 1m d 1. ethanol is added into ethanoic acid and shake/stir 1m [ volume ratio ethanol : acid = 2:1 ] 2. a few drop of concentrated sulphuric acid is 1m
  13. 13. Added 3. mixture is heated gently 1m H H H H H C–C=C–C H H H 2m H H H C–C=C–H H H C H H 0 Questio Suggested Answer marks n 2m H H H H H C=C-C–C H H H Total mark= 10m4) Natural rubber is a polymer, where the monomer is isoprene or 2- methylbuta-1,3-diene.Natural rubber is obtained from latex, which is a colloid made up of rubber particles and water.
  14. 14. No question Answers marks4) a) Structural formula of 1 isoprenei)ii) Labelled diagram of Correct latex particle in water diagram =1 Label = 1b Explain why latex in • Protein membrane of rubber particles are 1 the original form negatively charged does not coagulate • So, the particles repel each other and do 1 not collide/ the protein membrane do not breakc However, or when • Air contain bacteria which 1 latex is exposed to produce lactic acid /hydrogen air, coagulation of ions in latex latex occur. Explain 1 (3m) • The hydrogen ions neutralise the negatively charged membrane • Rubber particles * reject rubber 1 molecule or rubber polymers* become neutral and so they collide with each other 1 • The membranes break, rubber (4 marks molecules/ polymers combined * maximum 3) reject rubber particles*d The properties of natural rubber can be improved by treating it with sulphur.(i) Name this process Vulcanisation ( correct spelling) 1(ii) State ONE use of the For making tyres, mattress, foam, shoes or any 1 treated rubber above suitable answers Total= 10m
  15. 15. Scheme answer no 5 Questio Suggested Answer marks n 5a. Heat change when 1 mole of Barium Sulphate form from its ions 1m b Ba 2+ + SO4 -2  BaSO4 1m c White observation forms or The containers become warm 1m d.i Heat release = 100 x 4.2 x (34.5- 29.5) J = 2100J 2m ii Mole of BaSO4 = 50 x 1.0 /1000 1m = 0.05 iii 0.05 mole BaSO4 - 2100 J 1m 1 mole BaSO4 - 1/ 0.05 x 2100 J - 42000 J 1m ∆ H = -42kJ mol-1 e Ba 2+ + SO4 -2 Energy ∆ H = -42 kJ mol-1 2m 4 BaSO Total 10m

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