Chemistry - ES, A, PR

Chemistry, innit.

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4 bonding pairs is tetrahedral,
3 bonding 1 lone, pyramidal,
2 bonding, 2 lone, bent
3 bonding pairs is planar triangular,
2 bonding, 1 double, planar triangular,
2 bonding pairs is linear,
1 triple, 1 bonding linear,
2 double bonds is linear.
Titrations - KIARC
A KNOWN volume of a solution of unknown concentration is added to a conical flask using a
graduated pipette.
Suitable INDICATOR is added, and the flask in placed on a white tile.
An ACID of known concentration is added from a burette, with constant swirling.
REPEATS are conducted, with the acid being added drop-wise as the endpoint is approached.
This continues until CONCORDANT values are obtained.
First Ionisation Enthalpy: the amount of energy required to remove one electron from each
atom in 1 mole of isolated gaseous atoms.
General FIE equation: X(g) ---> X+(g) + e-
Trends in FIE graphs:
On the graph, the elements at the peaks are the noble gases. This is because they all have
full outer shells of electrons, and are therefore very unreactive so difficult to ionise.
The elements at the troughs are the Group 1 elements; they have only one outer electron
so are very reactive and easily ionised.
Trends in FIE in the periodic table:
Across a period, FIE increases as the nuclear charge of the element increases but electrons
are being added into the same shell, so they are all held more strongly by the increasingly
positive nucleus, and are therefore more difficult to remove.
Down a group, FIE decreases as there are more filled shells between the nucleus and the
outermost electrons, and the filled shells shield the positive nucleus from the outer
electrons, so they are more easily removed as they're held less strongly.
Also, successive ionisation enthalpies are always higher than the first.
This is because, after 1 electron have been removed, the rest are held more strongly by the
nucleus and are therefore more difficult to remove.
If electrons are being removed from the next shell, there is an even bigger increase in
ionisation enthalpy as electrons held in shells closer to the nucleus are obviously held more
Some ions you should know:
SO4 2-

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CO3 2-
To remember them, I made up this weird thing; No, oh ho.. so co!
And then NH4+ is just memorable.
So like, the first three before the pause are all 1-, and those after the pause are 2-. Anyway it
works for me 'cause I made it up, but it might not be useful to you. But there ya go.
To draw a hydrated ion, label the charge on the ion and show the polarity on the water
molecules surrounding it.…read more

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F -1 (except in OF2)
Cl -1 (except when combined with O or F)
O - 2 (except in O2-)
H +1
For concentration calculations, remember the triangle:
The units for volume should always be in dm^3, and to convert between cm and dm, divide
or multiply by a 1000.…read more

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The halogens exist as diatomic molecules, with the bonds between the two atoms (the
intramolecular bonds) being covalent, and the bonds between the molecules (the
intermolecular bonds) being instantaneousdipole-induced dipole bonds.
As you go down the group, the diatoms become larger and have more electrons, which
means the intermolecular bonds are stronger. This is why the physical states go from gas to
solid as you go down the group, i.e.…read more

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Storage and transport of Halogens.. here comes the extra boring bit.
Fluorine is too reactive to store, and so is made on site as and when needed by electrolysing
liquid hydrogen fluoride.
Chlorine is a highly toxic gas, and as such is transported by rail or road tanker as a liquid.
Bromine is transported in lead-lined steel tanks. Transport routes are planned to minimise
the risk of accidents, for example, routes are planned to avoid residential areas.…read more

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Preparation of halogenoalkanes - SSDD
Reaction is carried out in a separating funnel.
1) SHAKE with sodium hydrogencarbonate solution to remove any acidic impurities.
2) SEPARATE from other immiscible liquids using a separating funnel.
3) DRY with anhydrous sodium sulphate.
4) Use simple DISTILLATION to collect the pure product.
Shake, separate, dry, distill!
It's like when you dry your hair.
First you shake your head to remove excess water, then separate with a comb, then dry
with a hairdryer..…read more

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Nucleophile Equation
HOH R-Hal + H2O ---> ROH + H- + Hal- (alcohol)
OH- R- Hal + OH- ---> ROH + Hal- (alcohol)
NH3 R-Hal + NH3 ---> RNH2 + H+ + Hal- (amine)
Reaction conditions for above:
1) heat under reflux
2) heat under reflux with aqueous sodium hydroxide and ethanol solvent
3) heat with concentrated ammonia solution in a sealed tube
Batch & Continuous processing
Batch: the reactants are placed in a vessel to react, and once the reaction has taken place,
the…read more

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The CFC story
CFCs have a lifespan of over 100 years in the troposphere and are very reactive.
The problem is that they photodissociate to produce chlorine radicals which deplete ozone.
-Joe Farman discovered a whole in the ozone layer using UV spectroscopy.
- NASA computers treated the low readings of ozone as anomolies.
- Conclusive evidence of the effect of CFCs was when an aircraft flew through the
stratosphere and measured ozone levels.…read more

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The atmosphere - TSI
Troposphere, Stratosphere, Ionosphere.
Troposphere comprised of:
- 78% Nitrogen
- 21% Oxygen
- 1% other (argon 0.93% and carbon dioxide 0.038%)
To convert from ppm to percentage, divide by 10,000.
e.g. 500ppm = 0.05%
Energy interacts with matter
Quantised energy levels - TRoVE
- translational: molecule moves around as a whole
- rotational: molecule rotates
- vibrational: molecule's bonds vibrates
- electronic: electrons move from one energy level to another.…read more

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Dynamic equilibrium: when the forwards reaction and backwards reaction are happening at
the same rate in a closed system, with the product:reactant ratio remaining constant.
Le Chatelier's principle: if a system is at equilibrium and a change is made to it, the system
will respond to counteract that change as much as possible.…read more



"excuse the shxt *** drawing" LOOOOOOOOOOOOL

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