NATIONAL 5 CHEMISTRY

Transcription

1 Farr High School NATIONAL 5 CHEMISTRY Unit 2 Nature s Chemistry Exam Questions (UPDATED MAY 2017)

2 Homologous Series 1. A 2. B 3. C 4. D 5. C 6. D 7. C 8. B 9. C 10. A 11. A 12. D 13. (a) F (b) B and D 14. Presence of carbon monoxide/ CO present/ 5% CO present 15. 2,3-dimethylbutane/2,3 dimethylbutane/2-3 dimethylbutane/23-dimethylbutane Accept loose spelling of methyl and butane but ane must be present Accept (di) 16. Full or shortened structural formula of cyclopropane (a) Same general formula and same/similar properties same/similar chemical properties Both required (b) (c) addition 19. (a) (b) 2-methylpropane-1-thiol 2methylpropane-1-thiol 2methylpropane 1 thiol (or any of the above without the 2) (c) Sulphur dioxide/so 2

3 20. (a) saturated Bromine decolorises No change Unsaturated (2) (b) Safety gloves Wash off any spills with sodium thiosulphate (c) Hexene or any isomer of hexene with double bond 21. (a) Tetrahedral Tetrahedron (b) (i) Allow shortened structural formula CF 3 CH 2 F or CHF 2 CHF 2 (ii) Chlorine/Cl/Cl 2 (iii) Shorter atmospheric life/biodegrades faster 22. (a) Man-made/made by chemists/scientists/man Does not occur naturally Not natural (b) (c) Glycerol/glycerine/Propan-1,2,3-triol 23. (a) A substance that is burned/combusts to produce energy/heat (burning and energy both required) any mention of molecule, element, hydrocarbon or compound will not conflict (b) (i) Above zero 35 If outwith range, check candidate s working (b) (ii) The smaller the number of carbons in the molecule, the more efficient/useful/better (the fuel) The smaller the structure/molecule, the more efficient/useful/better it is If a molecule has a branch/or methyl group in the hydrocarbon it is more efficient/useful/better (fuel) The more yl groups the more efficient The more complex, the more efficient/useful/better The less hydrogens the more efficient

4 24. (a) Ethyne/etyne (b) (i) Allow one missing bond (C-H) or allow one missing H Shortened structural formula accepted (b) (ii) Bromines are not attached to adjacent carbon atoms ` Bromines not beside each other/not together Bromines have hydrogen between them/hydrogen in the middle Bromines too far apart/not close enough to react 25. (a) Heat the catalyst and then the liquid paraffin/mineral wool or heat catalyst first (b) To prevent suck-back or some description (c) (i) Aluminium oxide/a1 2 O 3 / formula must be correct (Aluminium) silicate or other silicate (c) (ii) Allows reaction to occur at lower temperature Lower energy required/ Lower activation energy (d) Addition/ Bromination/ Halogenation/ Addition/ Brominisation 26. (a) 27. C 28. B 29. C 30. B Allow one slip: one missing bond but not in carbonyl group or one missing hydrogen Accept correct (partial) shortened structural formula (b) Heptan-4-one/heptan4one /heptane-4-one/hept-4-one/hept4one/hepta-4-one Must have hept, 4, and one (c) approx 150 or any number within the range 31. (a) They have similar chemical properties and They have the same general formula. Both required for 1 mark (b) Butane, or it, has stronger / more / bigger forces of attraction between molecules or mention of intermolecular attractions If neither of these two points are given a maximum of one mark can be awarded for Butane is bigger / has more carbon or hydrogens / longer carbon chain

5 32. (a)(i) The higher/lower the number of carbon atoms the higher/lower the flash point The flash point increases/decreases as the number of carbon atoms increases/decreases (a)(ii) inclusive (units not required) (b) 99 with no working (3) 33. C 34. D 32/128 = gives 2.25 (9 x 0.25) (this step on its own 2 marks) 2.25 x 44 = 99 (this step on its own 3 marks) g and 44 g both shown 128 g gives 396 g (9 x 44) (this step on its own 2 marks) 32 g gives 99 g [(396/128) x 32] (this step on its own 3 marks) g and 44 g both shown 128 g gives 396 g (9 x 44) (this step on its own 2 marks) 128/32 = 4 396/4 = 99 (this step on its own 3 marks) Any other valid method accepted. 35. (a) But-2-ene or 2-butene (b) (Molecules/compounds /hydrocarbons/alkenes) with same molecular/chemical formula but a different structural formula (c) Correct structural formula for 3-methylpent-2-ene or 2 ethyl but-1-ene or mirror images or correct shortened structural formula 36. C 37. B 38. B 39. C 40. (a) Methoxypropane (spelling must be correct) (b) C n H 2n+2 O C n H 2n+2 O 1 C n H n2+2 O (c) 1 st = weak, 2 nd = strong (both required for 1 mark) (d)(i) ethane/eth-1-ene ethylene (ii) Any acceptable full, shortened or abbreviated structural formula

6 Everyday Consumer Products 1. C 2. A 3. D 4. A 5. B 6. A 7. B 8. C 9. CH 3 CH 2 OH/CH 3 --CH 2 OH CH 3 CH 2 OH/CH 3 CH 2 --OH CH 3 CH 2 (OH) 10.(a) Hydration / Catalytic hydration (b) 11. (a) (b)

7 12. (a) Aluminium oxide (Al 2 O 3 ) If formula given, must be correct Steel wool Wrong formula, name correct (b) (i) Butene/C 4 H 8 Full or shortened structural formula accepted Allow one missing bond/h (b) (ii) (Bromine solution would) decolourise/change from brown to colourless turns bromine colourless loses colour allow follow through from b (i) ie no change/stays brown 13. (a) (b) Pentyl butanoate 14. (a) Starch + water glucose Ignore non conflicting additional information eg hot water in equation and mashing above arrow Reversible arrow acceptable If formulae is given, must be correct Mix of formulae and words is acceptable must be correct (b) Fermentation or Anaerobic respiration (c) Allow shortened structural formula CH 3 COOH Bond does not need to be shown between O and H Allow one slip eg missing bond (C to H), missing atom but not carbon to carbon bond or carbon atom

8 15. (a) (i) Fermentation/ Anaerobic respiration (ii) Enzyme/biological catalyst/enzyme protein Ignore names of enzymes given 16. C (b) Yeast is denatured/destroyed/loses its shape Enzyme is denatured/destroyed/loses its shape Yeast dies/is killed (c) Distillation Correct description of the distillation process to include both boiling and condensation stages Fractional distillation 17. (a)(i) Hydroxyl 18. A (ii) Any correct full or shortened structural formula for an isomer (iii) C n H 2n O 2 C n H 2n+1 COOH (b) ethanol propanoic acid Spelling of both must be correct 19. (a) Hydroxyl or OH or OH (b)(i) Butanoic acid or methylpropanoic acid or 2-methylpropanoic acid or butyric acid (ii) Bromine/Br 2 decolourised/discolourised or bromine/br 2 goes colourless 20. Carboxyl 21. (a) The correct structural formula for isoprene (b) Diagram showing delivery tube passing into a test tube which is placed in a water/ice bath. Delivery tube must extend close enough to the neck of the test tube to ensure the vapour can enter the test tube. (c)(i) addition/additional bromination (ii) C 10 H 16 Br hydroxyl

9 Energy from Fuels 1. (a) (b) 2800 to The energy of the products is less than the reactants Energy decreases from reactants to products therefore energy is lost Reactants have higher chemical energy 3. (a) Endothermic (b) E = mcδt 45 = ΔT ΔT = 53.8 o C (53 or 54) (Units not required) 4. (a) Answer within range to No units required (b) E = mcδt = = (units not required) 5. (a) Heat lost to surroundings Incomplete combustion (of alcohol) Ethanol impure Loss (of ethanol) through evaporation ANY TWO 6. C (b) (kj units not required, ignore incorrect units) Partial marks -- 1 mark for ratio 50/ or 50000/1.45 or or 34.5 appearing in working

10 7. (a) 2090 with no working = (3) E H =cmδt = 4.18x 25 x 20 =2090 (3) using concept cmδt with c = 4 18 using correct data ie 25 and 20 final answer 2090 If awarding partial marks, the mark for the final answer can only be awarded if the concept mark has been awarded (b) Produces SO2 / acidic gases / oxides of sulfur Produces acid rain 8. (a) Method B (it) Complete combustion/more oxygen/pure oxygen Less/no heat loss (to surroundings) Better insulation Metal/platinum is a better conductor or Method A Incomplete combustion Less oxygen (More) heat loss to surroundings No draught shield/no insulation Glass is a poor conductor Flame too far away from beaker or Any other reasonable answer 9. B (b) 14 /14 2/14 21/ with no working (3) Partial marking using concept cmδt with c = 4 18 To be awarded the concept mark candidates do not specifically need to write cmδt. The concept mark is awarded for using this relationship with values - three values, one of which must be 4 18 using data correctly i.e. both 0 1 and 34 C final answer 14/14 2/14 21/ If awarding partial marks, the mark for the final answer can only be awarded if the concept mark has been awarded. 10. (a) 1 mark for Method A. The second mark for the explanation cannot be awarded if the first mark is not gained. 1 mark for explanation of accuracy of A (or inaccuracy of B) based on Heat loss Heat transfer Mass loss (due to ethanol being combusted/used up) eg - Method A because more heat is transferred to water Method B because less heat is transferred to water B releases more heat to the surroundings

11 (b)(i) A statement that identifies the effect of changing the position on the energy released. eg If the alcohol is 2-ol then less energy is released compared with 1-ol or vice versa. As you move from one to two (carbon/position) then the energy decreases or vice versa. As it (the position of the functional group) increases/gets higher, the energy released decreases or vice versa Functional group (or it/hydroxyl/ OH) on (position) 1/end carbon/first carbon energy released is greater/higher/bigger/increases Functional group (or it/hydroxyl/ OH) on position 2/not on the end carbon energy released is smaller/lower/decreases As it/functional group goes further along/further down/further up the lower the energy or vice versa. (ii) (c) 55 or with no working 3 marks 1 mark for using the correct concept of T = Eh / cm with both 4 18 and 23 correctly substituted 1 mark for 0 1 with or without concept 1 mark for correct arithmetic (this mark can only be awarded if the concept mark has been awarded).