A2 Unit F325 - Equilibria, Energetics and Elements
Summary
Summary Chemistry A Level OCR
12 views 0 purchase
Course
A2 Unit F325 - Equilibria, Energetics and Elements
Institution
OCR
This slide show consists of all the topics and sub - topic the OCR exam board requires in only 76 slides.
Slides are straight to the point using key terminology which is exam specific.
Slides only take about 5 minutes to read saving you time and energy.
A2 Unit F325 - Equilibria, Energetics and Elements
All documents for this subject (40)
Seller
Follow
20arpanahim
Content preview
CHEM
YEAR 2
, ORDER OF REACTION
This is the exponent/number which describe the change in conc effect on initial rate of reaction
Sometimes increase in conc does not increase rate
0 order- conc has no effect - straight line across y axis
1st order - directly proportional conc and rate increases by the same number - straight line - y=mx+c line
2nd order - exponential if conc doubles rate gets squared shown by a exponential model graph- curved
2nd order - e.g. - if you triple conc rate of reaction increases by 3 squared (9) and etc
Overall sum of orders is when you just add the orders in a reaction together
Finding orders of reaction Finding order of initial B
E.g. So 0.4/0.1 = 4
Initial rate was 0.8 which times by 4 = 3.2
Hence this is a directly proportional relationship and is the 1st order
Finding order of A - changes between 2 and 3
Account for B first - doubles between 2 and 3 hence 3.2 should double
without A being involved - so it becomes 6.4
However it becomes 1.6 with A hence it is smaller by a factor of 4
As 6.4 divided by 1.6 = 4
As A halves rate becomes smaller by ¼ hence it is an exponential
relationship - 2nd order
If you account for A and B you will see no change in initial rate of
reaction when C changes conc between 3 and 4 hence is 0 order
, CONC Vs TIME GRAPHS
Straight line is order 0 curved line is order 1 even more exponential/ curved graph is order 2
To find gradient of the curve you draw a tangent then do the conc/time
To prove orders of reaction you find the gradient at 2 separate points and then compare the relationships with
respect to conc and time - e.g. if one halves and the other halves as well it is first order
, HALF LIFE
Finding t ½
-choose any point on
y axis
This is the time taken for a conc of a reactant to decrease by half -half it
Used in various practicals to deduce the order -its difference in time
is its half life
How to work out half life from graph
Choose a conc - in this case e.g. 1.2
Half the conc
See what time it is at in this case 0.6 conc = 60 sec
Half the conc again - 0.3
At 0.3 it is at 30 sec
-As time is getting halved each time conc is getting halved this is 0 order
Half life is written as t ½ decreases over time
-For 1st order time stays the same as conc halves and is t ½ stays
constant
-For 2nd order as conc halves time doubles which is written as t ½
increases over time
Equation to find the rate constant, K, can only be used for overall order of a 1st order of reaction
Equation = ln2 / t ½
T ½ of course is the half life in seconds for 1st order this is constant always
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller 20arpanahim. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $13.69. You're not tied to anything after your purchase.
