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Intermediate 2 Chemistry


                                  Intermediate 2 Chemistry. PPA Revision

Unit 1                                       Unit 2                           Unit 3

Effect of Concentration on the Rate of       Testing for Unsaturation         Preparation of a Salt
Effect of Temperature on the Rate of         Cracking                         Factors which Affect Voltage
Electrolysis                                 Hydrolysis of Starch             Reaction of Metals with

 Unit 1
Effect of concentration on rate.
Often called the iodine clock reaction.
Persulphate and potassium iodide
Rate is the inverse of time. Unit s-1
All other factors must be kept the same.
The change is sudden due to presence of Iodine the starch changes colour turns black.
Easily measured change
Safety, eye protection and care not to come in contact with the skin

Effect of heat on rate
Thiosulphate on a cross, add Hydrochloric acid.
Forms fine powdered (colloidal) sulphur. Which obscures the cross
Errors include when exactly does the cross disappear.
Keeping temperature constant is difficult

Electrolysis of copper(II) chloride
Watch the animation
Danger of Chlorine, a toxic gas
Electrolysis cell 2 carbon electrodes
One turns brown –ve
One a gas is evolved +ve
Moist universal indicator paper turns red.
Smell Very carefully

Unit 2
Testing for unsaturation.
Small amount of hydrocarbon
Add bromine water
Shake by waggling, do not allow any chemicals in contact with the skin.
Alkenes turn the bromine water from brown to colourless(not clear)
Mineral wool and paraffin                                                                                        Gas
                                              Rocksil wool
Catalyst aluminium oxide                      soaked in
Heat in a tube.                               paraffin         Heat

Gas given off, therefore smaller molecules
Decolourises bromine water therefore unsaturated
Do not stop heating until you have removed the tube from the water, suck back shatters the tube.
Hydrolysis of Starch
Enzyme is amylase
Experiment conducted at 37oC
Benedicts solution shows that a simple reducing sugar is produced after 5 mins, colour change blue to orange
Repeat at high temperature using Hydrochloric acid
Acid must be neutralised before testing with sodium hydrogencarbonate

Unit 3
Preparation of a salt.
Insoluble magnesium carbonate is used so that it can be filtered off after reaction stops
No more gas given off shows reaction has stopped
Volume of water reduced by heating, boiling causes splashing
Note the shape of all the crystals is the same

Factors affecting Voltage
Keep all parameters the same except the one you are measuring and the one you are changing.
Metals, concentration of solution, solution used, volume of solution, how far apart the electrodes, are how
deep in the solution the electrodes are, are all possible measurable variable
Repetition is a way of verifying that the results are correct.

Reaction of metals with oxygen
Potassium permanganate is a source of oxygen.
Heating the metal in a stream of oxygen causes it to react,
The higher the metal is in the ‘Electrochemical Series’ Page 7 data book the more reactive it is.
Magnesium burns very brightly.
Danger test tube must never point at anyone but across the bench.

                                    Mineral wool

                                                       Test metal

General Safety Considerations
Always wear safety specs.
Be aware of danger labels
Never touch chemical with bear hands
Always read safety labels
Know what the dangers are before conducting an experiment
Heat makes ant chemical unsafe
Never sit when conducting experiments

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