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

Completed!
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

HideShow resource information
Preview of COMPLETE - A2 - Chemistry - Unit 4 - Edexcel - New Spec 2008

First 181 words of the document:

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)
clock reaction (sudden change at particular time means specific concentration of product has
been reached - the shorter the time taken, the faster the rate)
electrical conductivity (number of ions will change as reaction occurs)
Concentration-Time Graph
Rate at any point can be found by drawing a tangent at that point on the graph and finding the
gradient.
Orders of Reaction
The order of reaction = how the reactants concentration affects the rate
INCREASE REACTANT ­ RATE STAYS THE SAME ­ ORDER OF 0
INCREASE REACTANT ­ RATE INCREASES BY 1 FACTOR ­ ORDER OF 1
INCREASE REACTANT ­ RATE INCREASES BY 2 FACTORS ­ ORDER OF 2
You can only find the order of a reaction *experimentally* ­ there is NO theoretical order system.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Shapes of Rate-Concentration Graphs tell you the order.
ZERO ORDER FIRST ORDER SECOND 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 = second order
You can also calculate the half life using reaction rates.…read more

Page 3

Preview of page 3

Page 4

Preview of page 4

Here's a taster:

EXAMPLE
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)
How to calculate rate constant from the orders and rate?
Rearrange to make k the subject and calculate.…read more

Page 5

Preview of page 5

Here's a taster:

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 order 0 with respect to
iodine.
Rate is proportional to [H+] so the reaction is of order 1 with respect to [H+].…read more

Page 6

Preview of page 6

Here's a taster:

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 halogens are much more
electronegative than the carbon so they draw in electrons making the Carbon slightly/delta positive.…read more

Page 7

Preview of page 7

Here's a taster:

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:
1) As EA increases, k will get smaller. Therefore large activation energy, means a slow rate ­ this
makes sense!
2) As T increases, k increases.…read more

Page 8

Preview of page 8

Here's a taster:

Catalysts
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 specificity to the reactions they catalyse.
There are two types of catalysts:
HOMOGENOUS CATALYSTS HETEROGENOUS CATALYSTS
These are catalysts in the same state as the These are catalysts in different physical states to
reactants.…read more

Page 9

Preview of page 9

Here's a taster:

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 the
particles can be arranged in lots of different ways.
SOLID LIQUID GAS
No randomness, therefore Some randomness, some Most randomness, highest
lowest entropy. entropy. entropy.
e.g. S (H2O(s)) = 7.4 JK-1mol-1 e.g.…read more

Page 10

Preview of page 10

Here's a taster:

Here, the products have high entropy states (e.g. gas) and there are more moles (e.g.…read more

Comments

Abdul

This is epic. You're AWESOME :)

abdul

really helpful, thanks

sophie

Great revision notes thankyou :)

EmmaBunting

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

n

great notes thanks 

Dominic_Sargent

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

spidermonkey

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

Similar Chemistry resources:

See all Chemistry resources »See all resources »