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Chemistry Revision Notes

C3-1: The Periodic Table

1.1

In the 19th century scientists didn't know much about the structure of atoms. Scientists tried to
categorise elements based on their properties and their atomic weights.

1863 Newlands proposed the law of octaves (similar properties repeated every 8th element) But
after calcium…

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are good conductors of heat and electricity. They react slowly or not at all with oxygen and water at
normal temperatures and they are strong and dense and used as building materials, often as alloys.

They form positive ions with various charges (Fe2+, Fe3+..)

Their compounds are usually brightly coloured…

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Temporary hard water contains hydrogencarbonate ions which decompose when heated to produce
carbonate ions, water and carbon dioxide. The carbonate ions react with the calcium/magnesium ions
in the water to produce precipitates of calcium/magnesium carbonate that are deposited as scale.

Another method is an ion-exchange column packed with resin containing…

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3.3

We can show the energy changes for chemical reactions on energy level diagrams. The difference
between the energy levels of the reactants and the products is the energy change for a reaction.
During a chemical reaction the reactants must break their bonds, breaking bonds is endothermic
because energy is…

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To find the difference between Aluminium, Calcium and Magnesium add excess sodium hydroxide
solution and the precipitate of aluminium hydroxide dissolves.

4.2

There are three tests for negative ions:

1. Carbonate ions: Add dilute hydrochloric acid to the substance to see if it fizzes. If it does and
a gas…

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If we know the volume of a solution and its concentration we can work out the mass or the number of
moles in the substance in any volume of solution.

Question examples:

1. 50cm³ of solution was made using 5.6g of potassium hydroxide (KOH). What is its
concentration in

g/dm³?…

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In a closed system no reactants or products can escape. Equilibrium is reached when the rate of the
forward action is equal to the rate of the backwards reaction, but the amounts of the amount of
product and reactant remains constant.

To change the amount of product or reactants the…

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The lower the temperature the greater the yield of ammonia, however at lower temperatures the
rate of reaction slows and an iron catalyst becomes ineffective so it would take longer to produce
ammonia. Therefore a compromise of temperature is usually between 200-450°C.

C3-5: Organic Chemistry

5.1

Organic molecules form the…

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Acids that don't ionise completely are known as weak acids. In aqueaous solutions of equal
concentration, weak acids have a higher pH and react more slowly than strong acids.

Esters are volatile compounds and have distinctive smells that may be pleasant and fruity so are used
in perfumes.

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