National Chemistry

2000 Credit ANSWERS

 

 

1.  (a)  D and F    (1 mark)

(b)  C and E   (1 mark)

(c)  B and E   (1 mark)

 

2.  (a)  B and C   (1 mark)

(b) C    (1 mark)

 

3.  (a) A    (1 mark)

(b) D    (1 mark)

 

4.  A and C    (1 mark each)

(if you pick three then lose a mark for the extra answer)

5. (a) D    (1 mark)

(b) A and F   (1 mark each )

(if you pick three then lose a mark for the extra answer)

 

6. A and D    (1 mark each )

(if you pick three then lose a mark for the extra answer)

 

7.  (a) B and F   (1 mark each)

(b) C    (1 mark)

 

8. (a) D    (1 mark )

(b) B and E   (1 mark each)

(if you pick three then lose a mark for the extra answer)

 

Part 2

 

9.  (a) aluminium is less dense /lighter

(b) iron is stronger; to strengthen the wire

 

10. (a) number of protons  = 14, 14, 14

      number of neutrons  = 14, 15, 16

(b) isotopes

(c) 28

 

11. (a) naphtha

(b) larger or heavier or longer molecules

(c) (i) to produce more of the useful fractions needed

     (ii) use at lower temperature

to get different products

possible

 save energy/less expensive

 

12.  (a)

  <IMG SRC="methcynmonomer.gif"

(b) carbon monoxide;  or HCN        

 

13. (a) SiO2

(b) chlorine

Write in words as you could easily ice the wrong formulae. Silly to know the answer but get it wrong because the formula is not correct.

(c) distillation

(d)  view

(e) SiCl4 + 2H2 -----> Si + 4HCl

 

14. (a) to complete the circuit

   to allow ions to flow between the beakers

(b) tin bromide; tin chloride; tin iodide; tin sulphate

(c) lead; copper ; silver

 

15.  (a) 20.8 %     ie             12.5        x   100

                                                 60

(b) to make sure all of the oxygen is used up - not all will have reacted in the first

pass.

All of the oxygen will be used up when there is no  further decrease in the volume.

 

(c) Carbon would catch fire;

      Carbon would produce a gas

 

16. (a) to allow electrolysis to happen;

to break down the substance;

to make the electrodes positive and negative;

to attract ions to the electrodes

(b) across axes must be labelled and include units aye (min"

up axes must be labelled and include units "volume of gas (cm3)

scales must be on across axes

scales must be on up axes

dots should be accurate

dots must be joined

at least half graph paper must be used (each error loses half mark)

(c)    16cm3

(d)   2H+         +      2e ----> H2

 

17.  (a) Haber

(b) Ammonia is broken down at high temperatures;

Less ammonia produced at high temperatures

(c) Ammonia is used to manufacture fertilisers required to enable more food to be grown for a larger population.

 

18. (a)  Molecules which have - a general formula;

   similar chemical properties

    gradual increase in physical properties

(b) Underline the chemicals mentioned in the question

 ie propane     C3H8       -----> water    H2O

Write under this the number of moles

                            1 mole ----->   4 mole

Write under this the mass of these moles

                                 44g ----->       4 x 18 = 72g ;                  (1 mole of water = 18 g)

So 44g of propane produces 72 g of water

therefore 22g of propane produces 36 g of water

 

19.  (a) Add iodine to the water - it would not turn black (as no starch passed  through tubing)

(b) (i) (large molecule) broken down by water

(ii) Add starch and amylase solution to the visking tubing

     (close visking tubing up)

     Place the visking tubing into the test tube of water

     (leave to react)

   Test the water in the test tube with Benedict's solution

    This should turn orange indicating the presence of reducing sugar/glucose/ hydrolysed

starch

 

20. (a) fermentation

(b) (i) As the number of carbon atoms increases then the heat released increases.

      (ii) 3265 to 3365  (the figures go up 641, 650 and 648 respectively - therefore the next figure would go up a similar amount 600 to 700 seems a  reasonable spread)

2000 CREDIT

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