National Chemistry

2002 Credit First thoughts

1. (a) What are the elements required by plants ?
(b) bases will neutralise acids.

2.(a) What type of bonding is present in sodium chloride ?
Then what are the conditions for conduction for that bonding ?
(b) molecules (moLOWcules) = low melting point therefore bonding is ?
Look for TWO substances with low melting point and the correct conditions for conductivity for covalent

3. (a) Identify which are metals to possibly be X.
Put the charge for each ion in the appropriate box.
(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
(a) What type of structure is required to decolourise bromine water - must appear in TWO boxes.
(b) You should know the definition of an isomer. match up the molecular formula.
Do not pick D

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

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

7. (a) Usually only talk about a reaction not occurring if there is an unreactive metal involved.
(b) For a reaction to form water Hydrogen and oxygen must be present in the reaction.
What other reactions make water ?

8. (a) Combustion is burning. What gas do things burn in ?
(b) TWO answers
Rusting is oxidation of iron. So B or F look likely to be involved.
What else occurs during rusting ?

9. TWO answers
Look at fluorine on page 1 of the data book. Pay special attention to the electron arrangement.

part 2

10. You should know two process associated with refining.
(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) What difference would this make to the diagram
(b) One of the first two carbohydrates in your list.

12. (a) (i) Do not change any of the formulae.
You need 4 x Cl on the right hand side.
(ii) Liquid at room temperature suggests 'low' melting point.
(b) Calculate mass of 1 mole.

13(a) Remember spectator ions are like pupils - they do nothing!
(b) One of the reactants (there are three) must be being oxidised. look on page 7.
 (c) (i) The labels needed are mentioned in the description of the experiment on the first line.
(ii) Sodium carbonate must cause a problem.

14. (a) Add something to the diagram to measure the volume of gas given off.
(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 and carbonate ion. keep the charges in.

15. (a) Which metal would be the easiest to get. The usual examples are not here.
Which method is the simplest ?
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

16. (a) first two lines tells you that glucose undergoes fermentation to produce alcohol plus a gas. (b) 15% alcohol concentration stops it - must prevent something happening
(c) (i) The main reactant is an alkene.
(ii) look at the example given. What change occurs when the product is formed?

17. (a) Write the molecular formula for each molecule in the boxes.
(b) Look at the structures of the alcohol and what is formed.
(c) Two metal suggest some kind of comparison using reactivity

18. (a) What is the advantage of using air and water.
(b) What is the formula of ammonia ? What elements are needed ?
(c) Acid + Alkali makes a salt
(d) (i) Pressure is the X axis but careful the question is about temperature and yield.
(ii) Might help with part (b)
Can something from the graph help

19. burette, numbers, titre - it is a titration calculation
(a)(i) The volumes are - 20.7, 20.0 and 20.2
(ii) Calculate the number of moles.
Use this average volume (or guess 20.7)
Moles and volume and ???? What is the missing number?
It is a volume of solution what wee calculation do you need ?
Obviously
  number of moles = volume and something

(b) You know the number of moles from part (ii) - (if not guess 5)

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