Page 177 - Chemistry

- To analyse and identify mixtures of substances which are difficult to separate by
other means
- Used to analyze dyes in food colouring (Any two each one mark)
8 a) Element R – Sulphur
b) Mix solid P oxide with water
put blue and litmus paper, Blue litmus paper remains blue, red litmus paper changes to blue.
Put blue and red litmus papers in water
Blue changes to red, red remain red.
9. 5 and 4 BOTH MUST BE CORRECT
10. EITHER
3
- In separate test tubes, boil about 5cm of each solution.
- Sodium hydrogencarbonate solution remains colourless forms no precipitate
- Calcium hydrogencarbonate solution changes from colourless to white precipitate
OR
2NaHCO 3aq Na 2CO 3 + CO 2(g)n + H 2O (e)
Ca (HCO 3) 2 (aq) CaCO 3(s) + CO 2 (g) + H 2O (e)
HEAT must be mentioned or implied.

11. a) * both axes labelled Boiling point ½
70 with units
Temperature / C
O

25 Room temperature
Melting point
15

Time (minutes)
b) Liquid
12. (i) Range of boiling points / no sharp boiling points
 1
 1
(ii) Carry out fractional distillation
13. (i) Evaporation

(ii) Uses a lot of fuel

(iii) Any soluble salt and water
14. Melting points is the specific √ ½ constant temperature√ ½ for a particular substance when a solid √ ½
change to a liquid√ ½
16. (a) To cool/condense vapour. √1 (1 mk)
(b) Water. √1 (1 mk) 3

(c) Blue solid √1 changes to white solid. √1 (1 mk)
17. (a) Solvent front √
(b) C √

18. a) Chemical √ ½
b) Physical √ ½
c) Physical √ ½
d) Chemical √ ½

19. - Smoky/ sooty √
- Not hot enough √

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