Higher Tier Chemistry Notes

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  • Created on: 29-05-13 18:07
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Chemistry Higher Tier
Understand the term mole as the Avogadro number of particles (atoms,
molecules, formulae, ions or electrons) in a substance
A mole is Avogadro's number simply because if you have 1 mole of an element its weight in
grams will be its atomic mass.
Understand the term molar volume of a gas and use its values (24 dm3 and 24,000
cm3) at room temperature and pressure (rtp) in calculations
In a gas: moles = or moles =
Calculate percentage yield
Percentage yield =
Theoretical yield is what you expect to get, for example if a reaction doesn't finish you may
end up with a lower yield.
To calculate theoretical yield it is important to understand that an equation gives you a ratio
of moles, e.g.Fe2O3 2Fe tells us that every one mole of iron oxide makes two moles of
iron. In this equation the weight of Fe will be your yield.
If you are told the weight of the Fe2O3 is 100g we can easily work out the theoretical yield:
Work out the moles of Fe2O3 by doing the weight (g) divided by the atomic mass:
100/160= 0.625Mol
You know that for every one mole of Fe2O3 there are two of Fe so we do:
0.625 x 2= 1.25 Mol
Now you have moles of Fe we can work out weight by Mol x Ar: 1.25 x 56= 70g
If you in fact got 82g of Fe you'd do (70/82) x100= 85.4%
Understand the relationship between ionic charge and the melting point and
boiling point of an ionic compound
The bigger the difference in charge, the stronger the attraction: if you have + and - atoms
they will have a weaker bond than +3 and -3 atoms. The stronger the attraction, the harder
it is to break the bonds, this means that the melting and boiling points will be higher. So the
bigger the charge of an ion, the higher the melting and boiling point.

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Describe an ionic crystal as a giant three-dimensional lattice structure held
together by the attraction between oppositely charged ions
An ionic crystal is a lattice of electrons in the shape of a cube, the ions are alternate positive
and negative and their opposing charges hold the structure together
Draw a diagram to represent the positions of the ions in a crystal of sodium
Draw diagrams representing the positions of the atoms in diamond and graphite
In diamond each atom is connected to 4 others,…read more

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Explain how the uses of diamond and graphite depend on their structures, limited
to graphite as a lubricant and diamond in cutting.
In Graphite the atoms from layers, these layers can slide over each other, this makes it very
slippery and so can be used as a lubricant.
Diamond is extremely hard because it has a many bonds in it; this means it is good for
cutting as it extremely hard.…read more

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Calculate the amounts of the products of the electrolysis of molten salts and
aqueous solutions.
One faraday is 96500 coulombs. It is also one mole of electrons.
If current of 0.2 Amps is passed through copper (ll) sulphate for two hours, how much
copper do you get?
Write out the half equation
Cu2+ + 2e > Cu
Work out coulombs of electrons flowing
Coulombs= current x time
Time is 2x60x60 (times 60 makes minutes, times 60 again makes it seconds)
Q= 0.…read more

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So bigger atoms (towards the bottom of the group) with the outer orbital far from the
nucleus will lose their electron more easily: this means they react more
Smaller atoms with the electron closer to the pull of the nucleus (at the top of group one)
will be less reactive as it takes more to lose the electron.…read more

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Conditions: sugar in water, yeast and a temperature of 30 C to 40 C.
As yeast is a living organism the optimum temperature for fermentation is 35 C. At higher
temperatures the reaction nearly stops as the enzyme is broken down or denatured.…read more

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Calculate molar enthalpy change from heat energy change
H =
Use average bond energies to calculate the enthalpy change during a simple
chemical reaction.
If we know how much energy is needed to break bonds and how much energy is released when new
bonds are made we can calculate the overall enthalpy change and find out if the reaction is
endothermic or exothermic.
We can carry out such calculations by using the bond energies.…read more

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Understand that some polymers, such as nylon, form by a
different process called condensation polymerisation
Two monomers join together when they lose a small molecule
made up of atoms from both monomers.
Understand that condensation polymerisation produces a small molecule, such as water,
as well as the polymer.
Commonly, an H atom from one and OH molecule from the other form water (hence
condensation reaction) and the two monomers become joined.…read more

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Vanadium (V) Oxide Catalyst
There is a 99.5% yield in this reaction
Step 3: Making the Sulphuric Acid
In principle, you can react sulphur trioxide with water to make sulphuric acid.
SO3(g) + H2O(l) H2SO4(aq)
In practice, this produces an uncontrollable fog of concentrated sulphuric acid. Instead, the
sulphur trioxide is absorbed in concentrated sulphuric acid to give fuming sulphuric
acid (also called oleum).
H2SO4(l) +SO3(g) H2S2O7 (l)
This is converted into twice as much concentrated sulphuric acid by careful addition of
water.…read more

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At the cathode
Both hydrogen and sodium ions are attracted to the cathode. However, it is much easier to
liberate the hydrogen ions.
2H+ + 2e- H2
In the solution
In the solution negatively charged hydroxide ions and positively charged sodium ions are
left. These form sodium hydroxide.
Na+ + OH- NaOH
This however is contaminated with sodium chloride when it leaves the diaphragm cell.…read more


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