Chemistry Unit 4 AQA notes

These are my half finished notes, hopefully what i've done is vaguely helpful. :)

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  • Created by: lucy
  • Created on: 01-03-12 09:36
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Rate equations
Rate=k [A]m [B]n
Where m and n are order of reaction (determined experimentally)) either 1, 2 or 0 and k is the rate
Increasing temperature would increase k because they are proportional as [A]m and [B]n are constant.
Rate determining step is the slowest step and the one that has all the compounds from the rate
equation in it.
Kc is the equilibrium constant calculated from equilibrium concentrations for a system at a constant
Kc= [Products]/ [Reactants]
Effect of changing temperature on Kc:
increase temperature for an EXOTHERMIC reaction (-ve H) decreases Kc
increase temperature for an ENDOTHERMIC reaction (+ve H) increases Kc
Any other change to equilibrium DOESN'T change Kc
Acids and Bases
Acids are proton DONORS
Bases are proton ACCEPTORS
pH= - log10[H+] [H+] = 10-pH Kw = [H+] [OH-]
Water is weakly dissociated
Weak acids and bases PARTIALLY dissociate. (Strong acids and bases FULLY dissociate)
Ka= [H+] [A-]/ [HA] Ka = [H+]2 / [HA] pKa = -log10Ka
Strong acid- strong base (equivalence = 7)
Strong acid- weak base (equivalence point <7)
Weak acid- strong base (equivalence point >7)
Weak acid- weak base (equivalence point is
Equivalence point is the point at which the solutions have been mixed in the right proportions
according to the equation.
A buffer solution is one that resists changes in pH when small quantities of an acid or an alkali are
added to it, or on dilution. Change pH by changing ratio of acid/alkali and the salt of that acid/alkali.
Acidic buffers work below pH 7 and alkaline buffers work above pH7. Uses of buffers include: blood,
shampoo and pH probes. pH of acidic buffers:
Ka = [H+] [Acid]/ [Salt]

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Nomenclature and Isomerism
Carbon atoms/name Prefix/ Suffix Example/functional group
1 Meth- Methanol
2 Eth- Ethanal
3 Pro- Propanone
4 But- Butanoic acid
5 Pent- Pentene
6 Hex- Hexane
Alkene -ene C=C
Arene Benz-/Phe- Benzene ring
Haloalkane Fluoro-/Chloro-/Iodo-/Bromo -F/-Cl/-I/-Br
Alcohol -ol/ Hydroxy- -OH
Aldehyde -al -C=O
Ketone -one -C=O
Ether -oxy- -O-
Carboxylic acids -oic acid -C=O
Ester -oate -C=O
Acid chloride -oyl chloride -C=O
Acid anhydride -oic anhydride -C=O
Nitrile -nitrile -CN
Amine -amine -NH2
Acid amide…read more

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Carbonyl Group
Aldehydes are readily oxidised:
Test (reagent) Result with Aldehyde present Result with Ketone present
Fehling's solution Brick red precipitate Remains Blue
Acidified potassium dichromate Orange to Green Remains Orange
Tollen's solution Silver mirror Remains colourless
Synthesis with HCN/KCN: CN is highly toxic and HCN is a gas so it's difficult to prevent it leaving the lab.
Reduction of Aldehydes and Ketones to alcohols. H- as nucleophile (nucleophilic addition with Cyanide
ion produces hydroxynitriles). Using NaBH4 as reducing agent.…read more

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Produces corrosive gas of HCL No harmful by products
Expensive (hydrolysis of sea water) Cheaper
High yield of aspirin due to dipoles Less yield of aspirin as less reactive
Aromatic Chemistry:
bond length is an intermediate between single and double bond (all same
Isomers the same (fewer isomers than expected)
Unreactive with electrophiles (no electrophilic addition-test with Br water)
Bond enthalpy of hydrogenation is -208 KJmol-1 not -360 KJmol-1 as expected
Bond angle is 1200
Delocalised ring gives stability to the molecule
Electrophilic…read more


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