National Chemistry

2002 Credit HINTS

1. (a) What are the elements required by plants ?
(b) bases will neutralise acids. What type of compounds react with acids?

2.(a) What type of bonding is present in sodium chloride ?
Ionic or covalent ?
Then what are the conditions for conduction for that bonding ?
Please note B and F have the same conditions AND so do C and E while you are looking for one answer.
(b) molecules (moLOWcules) = low melting point and covalent.
Look for TWO substances with low melting point and the correct conditions for conductivity for covalent
Please note B and F have the same conditions AND so do C and E and you are looking for two answers !

3. (a) Identify which are metals to possibly be X.
Put the charge for each ion in the box.
From the formula XY2 what charge do you want on the metal X and what charge on the element Y.
(b) What is the formula for methane ? What element makes the same number of bonds as the elements in methane ?
Molecule - just non-metals or metal and non-metal.

4. Write the molecular formula in each box
C4H10; C4H8; C4H8; C4H8; C3H6; C4H10
(a) What type of structure is required to decolourise bromine water - must appear in TWO boxes.
(b) Same molecular formula but different structure. Match up the molecular formula.
Do not pick D

5.(a) What are the charges on protons (+), electrons (-) and neutrons (neutral) .
Remember definition of why an atom is neutral. p=e
(b) Remember definition of isotope. What must they have the same ?

6. In the nucleide notation given what does number 6 represent ? Atomic number
How is number 14 calculated ? protons + neutrons

7. (a) Usually only talk about a reaction not occurring if there is an unreactive metal involved. eg Cu, Ag, Au
(b) For a reaction to form water Hydrogen and oxygen must be present in the reaction - so bomb out E.
D has water as reactant so will not be making it.
What other reactions make water ?

8. (a) Combustion is burning. What gas do things burn in ? It must be there as a reactant in at least two places.
(b) TWO answers
Rusting is oxidation of iron. So B or F look likely to be involved. Is one oxidation ?
What else occurs during rusting ?

9. TWO answers
Electron arrangement of fluorine is 2,7
Decide if each statement is true or false - in any order.

part 2

10. You should know two process associated with refining. Which makes ethene ? Think about its formula.
(b) (i) Look at the polymer structure and copy out what repeats itself.
(ii) look at the polymer structure. What could be produced by burning these elements ?

11. (The diagram tells you that starch is heated with hydrochloric acid. The result is then tested with Benedict's solution which turns red. Notice in part (ii) you are told that Ailsa thought that Glucose had been formed.
a) (i) What reaction changes starch to glucose?
(ii) You know another two.
(iii) The only change to the pictured experiment is that amylase is used instead of hydrochloric acid. The questions suggests that it is a surprise that this did not produce the same result.
Where does amylase come from ?
(b) One of the first two carbohydrates in your list. So how many carbons?

12. (a) (i) Do not change any of the formulae.
  TICl4 + H2O -----> TiO2 + HCl
  HCl
  HCl
  HCl

(ii) Liquid at room temperature suggests 'low' melting point. Suggest molecule
(b) Only 1 x Ti in TiO2 (mass of TiO2 is (1 x Ti)+(2 x O))

13(a) Remember spectator ions are like pupils - they do nothing! So score anything that appears on both sides then copy out accurately.
(b) One of the reactants (there are three) must be being oxidised. Look on page 7. Ie Cu or Ag+ or NO3-
Do not pick the one which does not appear on page 7.
 (c) (i) The labels needed are mentioned in the description of the experiment on the first line. 'copper displaces silver from silver nitrate'
(ii) Sodium carbonate must cause a problem. dealing with ions so try page 5.

14. (a) Add something to the diagram to measure the volume of gas given off. remember in diagrams - nothing open to the air and if liquid present draw it in.
(b) (b) label both axes; put on the scale; make sure over half the graph paper is used; make sure it is a line graph.

(c) Read it off of your graph - be accurate.
(d) formula for sodium carbonate - use sodium ion (on page 7) and carbonate ion (on page 4). Keep the charges in.

15. (a) Which metal would be the easiest to get. The usual examples are not here. Look at the data book which metals are easy to get ? Which of these three is closest to them ?
Which method is the simplest ? match these two up.
Now go for the hardest metals to get.
(b) What large hot thing is iron produced in ?
(c) step 1: copy out equation
Fe2O3 + 3CO -----> 2Fe + 3CO2

  step 2: underline what chemicals the question is interested in
  Fe2O3 -----> 2Fe
  step 3: write number of moles
  1 mole of Fe2O3 -----> 2 moles of Fe
  step 4: calculate mass of these moles
  (2 x Fe)+(3 x O) -----> (2 x Fe)
 

16. (a) first two lines tells you that glucose undergoes fermentation to produce alcohol plus a gas. The formula of glucose is C6H12O6 - what possible gases could come from this compound.
(b) 15% alcohol concentration stops it - must prevent something happening
(c) (i) The main reactant is an alkene; unsaturated; C=C double bond.
(ii) Look at the example given. What change occurs when the product is formed?
The double bond beaks; one carbon of the double bond gets another H; the other carbon of the double bond gets a OH.
Do the same to the molecule in question.

17. (a) Write the molecular formula for each molecule in the boxes. Just need the right hand side molecules as these are the aldehydes and ketones - so C2H4O; C3H6O; C3H6O and C4H8O -
(b) Look at the structures of the alcohol and what is formed. First two make aldehyde and second two make ketone. Why?
c) Two metal suggest some kind of comparison using reactivity.
Copper oxide is reduced to copper metal but, the question suggests, that aluminium oxide cannot be reduced to aluminium.

18. (a) What is the advantage of using air and water rather than other chemicals ?
(b) What is the formula of ammonia ? NH3
What elements are needed ? nitrogen and hydrogen
(c) Acid + Alkali makes a salt. The acid is phosphoric acid.
(d) (i) Pressure is the X axis but careful the question is about temperature and yield.
The yield increase/decreases/stays the same as temperature .......
(ii) Might help with part (b)
Can something from the graph help - temperature or pressure ?

19. burette, numbers, titre - it is a titration calculation
(a)(i) The volumes are - 20.7, 20.0 and 20.2 - not the odd one out!
(ii) use this average volume to calculate the number of moles.
It is a volume of solution what wee calculation do you need ?
Obviously
  number of moles = volume and something
 
  number of moles = volume and concentration

  ie concentration = mol
  litre
 
  You have the volume
  You are to calculate the number of moles
  Is there a concentration ? Look at the diagram.
(b) You know the number of moles from part (ii) - (if not guess 5)
Questions states 1 mole of acid reacts with 1 mole of hydroxide.
Therefore 5 mole of hydroxide .......

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