COMPLETE - A2 - Chemistry - Unit 4 - Edexcel - New Spec 2008

I used the specification as a tick-list, as well as my revision guide and standard textbook.

This is for the Unit 4 of Edexcel Chemistry A2 Level. Enjoy, and any feedback is very welcome.

(If you can't access it or something, message me, and I'll email you it)

Rate and/or comment :)

Rach x

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This is for the Unit 4 of Edexcel Chemistry A2 Level. Enjoy, and any feedback is very welcome.

4.1 Rates of Reactions
Reaction Rate = change in amount of reactants/products per unit time (units: mol dm-3s-1)

Following a reaction;

gas volume produced (gas syringe)
mass lost (balance)
colour change (colorimeter)…

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Shapes of Rate-Concentration Graphs tell you the order.


*square brackets indicate concentration. For example [X] = concentration of X.

Half-life = time taken for half the reactant to react

If the half life is constant = first order

If the half life is doubling…

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Propanone + Iodine --> Iodopropanone + H+ + I- (reaction occurs in acid)

Info: First order with respect to propanone and H+ and zero order with respect to iodine

Rate equation = k[propanone]1[H+]1[iodine]0

Simplify to;

Rate equation = k[propanone][H+] (because anything to the power of 0 is 1)


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*Reaction rates won't be exactly double or treble due to experimental errors etc.

4) Now we can work out the rate equation:

Rate is proportional to [propanone] so the reaction is of order 1 with respect to propanone.
Rate does not change/is independent of [iodine] so the reaction is of…

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Halogenoalkanes ­ Nucleophilic Substitution (SN)

Halogenoalkanes can be hydrolysed by OH- ions by nucleophilic substitution. This is where a
nucleophile (e.g. :OH-) attacks a molecule and is swapped/substituted for one of the attached groups
(e.g. Br -). In this case the Carbon (C+) to Halogen (X-) bond is POLAR as…

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Activation Energy

We can calculate the activation energy using the Arrhenius equation:

Where; (you don't have to learn this, just understand the relationship)

k = rate constant EA = activation energy (J)

T = temperature (K) R = gas constant (8.31 JK-1mol-1)

A = another constant

Some relationships to note:…

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Catalyst = increases rate of a reaction by providing an alternative reaction pathway with a LOWER
activation energy (EA). A catalyst will be chemically unchanged at the end of a reaction.

Adv: Small amount needed to catalyse a lot of reactions, also they are remade, thus reusable.

Disadv: High…

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4.2 Entropy
Entropy = a measure of how much disorder there is in a substance, how many different ways particles
can be arranged.

Systems are MORE energetically stable when disorder/entropy is HIGH.

EXAMPLE: A gas will want to escape its bottle because the room it's in is much bigger and…

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Here, the products have high entropy states (e.g. gas) and there are more moles (e.g. reactants to
products = 2:3) And so, overall entropy has increased = SPONTANEOUS (also depends on H ­ see



Ssys = Entropy change of a system, the entropy change between the…




This is epic. You're AWESOME :)



really helpful, thanks



Great revision notes thankyou :)



I only seem to be able to download Ch1- rates of reaction. Do you have the rest of the chapters?



great notes thanks 



Doing WJEC but these notes match up well, thankyou :)



Thank you for the notes. This helped me pass my A levels.

Much appreciated :)  

tinashe dongo


It"s somewhat precise and concise which is one of the most considered characteristic of a text book by almost all students

Samha Aminath


thanks a lot

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