C3 Exhaustive Revision Notes

These are my exhaustive revision notes for Chemistry Unit 3 of the GCSE Further Additional Science / GCSE Chemistry syllabus for Edexcel.

I have used multiple textbooks as well as internet sources to compile these notes, and whilst I was compiling them, I actively kept the syllabus at hand, so hopefully there is nothing beyond these notes which is essential knowledge in order to answer any question on the exam paper (I would promise, but I know everyone's liable to human error!).

I hope that you may find these notes useful :)

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There are two types of chemical analysis:qualitative analysis, which investigates which elements and compounds
are present in a sample, and quantitative analysis, which measures the amount of the aforementioned elements
and compounds which are present in said sample.
Chemical analysis is used principally in two industries: in the w
ater industry and in medical blood tests.
In the water industry, chemical analysis is used in order to ensure that drinking water is sufficiently pure
against government standards and not containing dangerous chemicals.
Aluminium salts are present in drinking water in order to remove small solids, although high levels of aluminium
have been linked to Alzheimers disease and damage to the digestive system. Sodium fluoride is also present in
drinking water because it reduces tooth decay.
In medical blood tests ,chemical analysis is used in order to monitor general health. This is because chemical
analysis in medical blood tests can diagnose certain diseases, such as:
Heart disease (indicated by high cholesterol)
Anaemia (indicated by low iron)
Kidney disease (indicated by high s
odium)
.
Chemical analysis in medical blood tests is also used by police forces in order to assess alcohol content in the
blood for suspects of drink-and-driving .
Ionic compounds are made of cations (positively-charged ions ) and anions (negatively-charged ions). In order to
identify an unknown ionic compound, qualitative analysis must be undertaken for both the anion and the cation,
because both of them are components of the unknown ionic compound .
Resultingly, the test for any ion must be unique in order to identify the ionic compound this is guaranteed
because different ionsreact differently to certain tests due to chemical differences.
Aluminium ,calcium , copper (II), iron (II) and iron (III) cations can be identified by adding sodium hydroxide
solution to ionic compounds containing them. The ionic compounds will react with the sodium hydroxide to form
an insoluble metal
hydroxide precipitate
, which will be unique in colour.
Symbol (all are in aqueous Colour of precipitate in reaction with sodium
Cation
solution) hydroxide
Calcium Ca2+
White
Copper Cu2+
Pale blue
Iron (II) Fe 2+
Green
Iron
Fe3+
Brown (rust)
(III)
Aluminiu
Al3+
White
m
Both calcium and aluminium cations form a white precipitate these can be distinguished from one another by
adding excess sodium hydroxide . In excess sodium hydroxide , the calcium cation precipitate will remain
unchanged, but the aluminium cation precipitate dissolves to form a colourlesssolution.
Ammonium cations (NH 4
+
) can be identified by adding sodium hydroxide solution to them and then gently heating
the solution. If the ammonium cations
are present, then alkalineammonia g
as will be given off.
Alkaline ammonia gas has a sharp, choking smell, but can be definitively identified through holding damp red
litmus paper to it ammonia turns damp r ed litmus paper blue.
Halide anions can be identified through reacting their ionic compounds with dilute nitric acid and then silver
nitrate solution they will produce an insoluble silver precipitate, which will be unique in colour. The dilute nitric
acid is used to remove any carbonate i
ons before the test.
Symbol (all are in aqueous Colour of precipitate in reaction with dilute nitric acid and silver
Anion
solution) nitrate

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Chlorid
Cl-
White
e
Bromid
Br-
Cream
e
Iodide I-
Yellow
Sodium , potassium, calcium and copper cations can be tested for using a flame test .A nichrome wire is dipped
into a concentrated acid such as hydrochloric acid and held in a flame until only a light orange colour is seen,
indicating that the nichrome wire is not contaminated . Then, the clean nichrome wire is dipped into the
concentrated acid again and them into a sample of the substance to be tested.…read more

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Ca(HCO3)2(aq)-> CaCO3(s)+ CO2(g)+ H2O(l)
The greatest disadvantage of softening temporary hard water through the thermal decomposition of the
calcium hydrogen carbonate is the formation of solid calcium carbonate, which can itself dissolve into water to
render it harder.Calcium carbonate is also the major component of limescale, the accumulation of which in pipes
can waste energyand block pipes.…read more

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V
In order to convert from mol/dm3
to
g/dm3
, a formula triangle akin to the one between
mass,moles and relative
formula mass can be used:
mass-concentration = mole-concentration x relative formula mass
g/dm3
= mol/dm3
x M
r
abbreviated to = c x Mr
A base is a substance with a pH value of more than 7 that can react with an acid in a neutralisation reaction to
form water and a salt.Bases dissolved in water are known as alkalis.…read more

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The process is different for the preparation of soluble salts from a soluble reactant ( alkalis). Unlike in the
preparation from bases , there is no visible indication with alkalis of when the acid has been completely reacted
because alkalis are not insoluble, so no s
olids accumulate.…read more

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When the direct current is active, the positively-charged cation in the ionic compound is attracted to the
negatively-charged cathode and the negatively-charged anion in the ionic compound is attracted to the
positively-charged anode .
At the cathode, the positively-charged cation is oxidised : this means that it gains electrons from the direct
current in order to become an atom .…read more

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Sodium chloride
Hydrogen Chloride
solution
Copper chloride solution Copper Chloride
Copper sulphate
Copper Oxygen
solution
Sodium sulphate
Hydrogen Oxygen
solution
Molten lead bromide Lead Bromide
Electrolysis can be used for copper purification when copper sulphate solution is electrolysed with copper
electrodes .
The anode begins as a huge lump of impure copper whilst the cathode begins as a small piece of pure copper .…read more

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The concentrations of each side are also constant.
Note that there does not necessarily need to be a 50/50 balance of reactants and products in a dynamic
equilibrium.
The position of equilibrium (that is, the relative amounts of reactants and products ) can be changed, most
especially by temperature and pressure . This is because, as Le Châteliers Principle runs, a system in dynamic
equilibrium will oppose any changes made to it.…read more

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The nitrogen used in the Haber Process is extracted from the air the hydrogen used in the Haber Process is
instead obtained from natural gas . The forward reaction i
sexothermic .
In the Haber Process , the hydrogen and nitrogen are fed into a mixer at a ratio of three to one. They are then
compressed in pressure in a compressor before being moved into a converter with iron catalysts , whereat they
react into ammonia.…read more

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Alkanes only contain single bonds between carbon atoms they are said to be saturated for this reason. Alkenes
contain at least one double bond between two carbon atoms they are thus instead said to be unsaturated .…read more

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