Farr High School

NATIONAL 5 CHEMISTRY

Unit 1 Chemical Changes and

Structure

Exam Questions

(UPDATED MAY 2017)

Chemical Changes and Structure PPQ answers Rates of Reaction 1. 32 – 10 = 2.75 (1) accept 2.8 8 2. scales correct and both labels and units correct (1) plotting of points and joining of points (1)

Max of 1 mark if bar graph/spike graph (labels, units and scale) or if both scales taken from table

Allow ½ box tolerance on plotting of points for each Allow 1 plotting error Axes can be reversed 3. Answer 0.0015 (1) Units not required 4. 0.017 (1) Units not required 5. D (1) 6. C (1) 7. A (1) 8. D (1) 9. (a) scales correct and both labels and units correct (1) plotting of points and joining of points (1) Max of 1 mark if bar graph/spike graph (labels, units and scale) or if both scales taken from table Allow ½ box tolerance on plotting of points for each Allow 1 plotting error Axes can be reversed (b) Must check reading from graph 0.5 tolerance (1) No graph drawn 34-35 (c) (2.2-1.2)/10 = 0.1 (1)

10. (a) points and line correct (1) (b) 1/0.0125 = 80secs (1) 11. A (1)

12. This is an open ended question 1 mark: The student has demonstrated a limited understanding of the chemistry involved. The candidate has made some statement(s) which is/are relevant to the situation, showing that at least a little of the chemistry within the problem is understood. 2 marks: The student has demonstrated a reasonable understanding of the chemistry involved. The student makes some statement(s) which is/are relevant to the situation, showing that the problem is understood. 3 marks: The maximum available mark would be awarded to a student who has demonstrated a good understanding of the chemistry involved. The student shows a good comprehension of the chemistry of the situation and has provided a logically correct answer to the question posed. This type of response might include a statement of the principles involved, a relationship or an equation, and the application of these to respond to the problem. This does not mean the answer has to be what might be termed an “excellent” answer or a “complete” one. (3)

13. 0·8 cm3s-1 or 0·8 cm3/s with no working (3)

For partial marking Maximum 2 marks for calculation. Final mark is awarded for the correct unit. 120 -96 96 - 120 90-60 or 60 - 90 or 24/30 (1) 0·8 (1) (this answer without working 2 marks) The mark for the correct unit, cm3s-1 or cm3/s or cubic centimetres per second or cm3 per second, is independent of the other marks. (1)

14. C (1) 15. (a) exothermic (1) (b)(i) 0.85 with no working (2) 29 – 12 or 12 – 29 30 – 10 10 – 30 OR (1) 17/20 0.85 (1)

(ii) Any value greater than 50 and less than or equal to 60. (1)

(iii) Faster / quicker / increase /speed up

Atomic Structure and Bonding Related to Properties of Materials

1. (a) (2) (b) (1) 2. (a) (1) (b)

3. (1) 4. (1)

Page 11

Question Acceptable Answer Mark Worth ½ Worth 0

4 (a) (i) (catalyst) in same state/form/physical state as

reactants ignore only reacts with chemicals in same physical state

1 or 0 Same state as products Same state as each other

(ii) RuCI2 Ru2+(Cl-)2 CI2Ru Ru1CI2

If ionic formula used it must be fully correct

1 or 0 RuCI2/RuCI2/incorrect symbol for Ru and/or CI formula with partial ionic formula Ru2+Cl-2

(b) (i) both labels and units correct ½

scale on X and Y axis ½ plotting of points ½ joining of points ½ -½ if not used at least half the graph paper -½ if line not through origin Max of 1 mark if bar graph or spike graph (labels, units and scale) or if both scales taken from table Allow ½ box tolerance on plotting of points for each Allow 1 plotting error Axes can be reversed 0,0 does not need to be marked on scale

2

(ii) Must check reading from graph 0.5 tolerance No graph drawn 34-35

1 or 0

5. (1)

6. sodium phosphate (1) 7. (a) (1) (b) (1) 8. (a) (i) (1) (ii) 34 (1) (b) 64 (1) 9.

(1) 10. (a) (1) (b) (1) 11.

(1)

12. (1)

13. (a) (1) (b) (1) (c) (1) 14. (a) (1) (b) 20 (1) 15.

(1) 16. (1) 17. D (1) 18. (a) Repulsion/repelled by nucleus/positive nucleus/protons/positive protons/positive

particles in nucleus or in atom of gold/like charges in nucleus, atom or gold (1) (b)(i) protons – 79, electrons – 79, neutrons – 118 (All for 1 mark)

(ii) Same atomic number / protons AND different mass number / mass / number of neutrons Atoms of the same element with different mass number / mass /number of neutrons

Candidate must specify either same atomic number or number of protons/positive charges

or atoms of the same element AND different mass number/mass/number of neutrons (1)

19. (a) (From top to bottom)

Covalent network – ionic lattice – metallic lattice – (discrete) covalent molecular)

(All 4 correct = 2 marks, 2 or 3 correct = 1 mark, 1 or 0 correct = 0 marks)

(b) delocalised/able or free to move or correct description (mention of ions = incorrect) (1)

20. A (1)

21. B (1)

22. D (1)

23. C (1)

24. D (1)

25. C (1)

26. (1)

27. (a) 2, 8, 6 or a correct target diagram (1)

(b) Mg(g) → Mg+ (g) + e- Mg → Mg+ + e Mg(g) → Mg+ + e- Mg → Mg+ (g) + e Or Mg(g) - e- → Mg+ (g) etc. (1)

(c) Decreases or

As you go from lithium to potassium (alkali metals) it (ionisation energy) decreases. or As you go from fluorine to bromine (halogens) it (ionisation energy) decreases. or as the atomic number in the group increases it decreases (1) 28. (a) carbon monoxide or CO/2CO (1) (b) covalent

29. D (1) 30. D (1) 31. B (1) 32. B (1) 33. C (1) 34. (a) (i) (1) (ii) (1) (b) 14.5 (1) (c) pyramidal OR trigonal pyramidal (1) 35. (a) unreactive OR does not react with water/air/alkalis/(almost all) acids OR can be

beaten into shape OR found uncombined (1) (b) 118 (1)

(c) (i) CO + O2 → CO2 OR CO + O2 → CO2 (1)

(ii) catalyst OR catalysis OR speeds up the reaction OR allows less energy/heat to be used for the reaction OR lowers activation energy (1)

Au

Formulae and Reaction Quantities 1. (1) 2. (a) (1) (b) (2) 3. (2)

4. (a) (1) (b) (1) 5. (a)

(1) (b) (1) 6.

(1) 7. (1)

8. (a) 25g (1) (b) (1) 9. (2) 10. (1) 11. A (1) 12. C (1) 13. (a) Potassium is an essential element or humans/human body cannot store it/have no

mechanism for storing it (b) 0.022 or 0.02 (moles) with no working (2)

0.86 / 39 = (1) 0.022 or 0.02 (moles) (1) (c) lilac/purple (1) (d) K+ NO3

- (both charges must be shown) (accept the use of brackets that do not negate) (1)

14. C (1) 15. B (1) 16. A (1) 17. (a) 3 (1) (b) (Fe3+)2(O

2-)3 OR Fe3+2O

2-3 OR (Fe3+)2O

2-3 OR Fe3+

2(O2-)3 OR Fe2

3+O32 (1)

(c) exothermic or exothermal (1) 18. (a) Boil it or boil off the water or heat it or leave it for some time/overnight/next lesson or

leave it on the window ledge or use Bunsen (burner) or appropriate diagram (1) (b) 0·2 with no working (2) ………………………………………………………………

Partial marking 3·19/159·5 = 0·02 (1) 0·02/0·1 = 0·2 (1) (this step on its own 2 marks) or (3·19 in 100 cm3) 31·9 in 1000 cm3 or 1 litre (1) 31·9/159·5 = 0·2 (1) (this step on its own 2 marks)

19. A (1) 20. 0.36 with no working 2 marks …………………………………………………………

0.01 moles gives 0.015 moles (1)

0.015 x 24 = 0.36 (1) (this step on its own 2 marks)

21. H3PO4 + 3NH4OH → (NH4)3PO4 + 3H2O (1) 22. 0.02 (1) 23. FM = 232·5 (1)

200·5/232·5 x 100 = 86·2% or 86% (1)

86·2% or 86% on its own 2 marks Use of atomic numbers max 1 mark, must have working to gain the mark, 83·3% Metal other than Hg max 1 mark

24. 25. 26. 70 with no working (3)

GFM = 160g (1) 112/160 x 100 (1) = 70 (1) 27. 17 or 17.28 or 17.3 with no working 3 marks ……………………………………………… GFM 162 (1) 28/162 x 100 (concept mark) (1) 1 mark for correct arithmetic

Acids and Bases

1.

(1) 2. (a) (1) (b) Spectator ions/spectate (1) 3. a higher (1) 4. Copper carbonate CuCO3 (1) 5. Neutralisation (1) 6. (a) Red/pink/orange/yellow (1) (b) (1) 7. D (1) 8. A (1) 9. A (1) 10. A (1) 11. (a) Paper X − Blue; Paper Y – Red Both correct (1) (b) Ammonium chloride (correct formula accepted) (1) 12. (a) 16 (1) (b) 0.08 with no working = 3 marks 0·1 x 0·016 = 0·0016 (1)

0·0016/2 = 0·0008 (1) 0·0008/0·01 = 0·08 (1) 0·08 on its own 3 marks or 0·1 x 16 = C2 x 10 (1) 2 1 0·8 = C2 x 10 (1) C2 = 0·08 (1) or any alternative correct method

13. C (1) 14. A (1) 15. D (1) 16. A (1) 17. B (1) 18. B (1) 19. (a) 1st = hydrogen, 2nd = hydroxide (both required for 1 mark) (b) It/calcium oxide is a base or

forms an alkaline solution (alkali) when dissolved in water. For the mention of alkali the candidate must explicitly state the calcium oxide is in solution/dissolved in water (1) Mention of it neutralising sulfur dioxide/it neutralises it/or a neutralisation reaction takes place. (1)

20. (a) 16 (b) 0·0032/3·2 x 10-3 with no working or correctly rounded answer (3) …………………………………………………………

Partial marking 0·0050 x 0·016 = 0·00008 mol I2 (1) 0·00008 mol of Vit C (1) (this step on its own gets 2 marks) 0·00008/0·025 = 0·0032/3·2 x10-3 (1) (this step on its own gets 3 marks) or 0·0050 x 16 = 0·08 mol I2 (1) 0·08 mol of Vit C (1) (this step on its own gets 2 marks) 0·08/25 = 0·0032/3·2 x 10-3 (1) (this step on its own gets 3 marks) or C1 x 25 = 0·0050 x 16 (1) 1 1 (1) C1 x 25 = 0·08 (this step on its own gets 2 marks) C1 = 0·0032/3·2 x 10-3 (1) (this step on its own gets 3 marks) or C1 x 0.025 = 0·0050 x 0.016 (1) 1 1 (1) C1 x 0.025 = 0·00008 (this step on its own gets 2 marks) C1 = 0·0032/3·2 x 10-3 (1) (this step on its own gets 3 marks) OR ANY OTHER ACCEPTABLE METHOD

21. C (1) 22. (a) Weak acid, strong base/alkali (both required for 1 mark) (b) 15.0 (1)