# Unit 2 - Physical Chemistry

Equilibrium, Le Chatelier and Equilibrium Constant K
http://www.chemguide.co.uk/physical/equilibria/change.html

Partition coefficient
To explain this further I have worked through an exam question on this .. hope this helps you to clarify it a little ...

Here is a bit of extra calculation ...

Working out pH of Acids and Alkalis At Higher you need to know how to work out the pH from the concentration of Hydrogen ions, however the answer is usually a round number such as pH3. Or you may have to estimate pH within a range from a concentration so the answer might be for example - "between pH3 and pH 4"
Just out of interest (so will not come up at Higher) if you wanted to work out an exact pH (such as pH 3.5) or an exact concentration from a pH such as 3.5 then you need to use the "Log" button on your calculator which helps you work out values that are on a logarithmic (or exponential) scale. For some details read here :

Ionic Product of Water KW and also temperature effects on pH of water
http://www.chemguide.co.uk/physical/acidbaseeqia/kw.html

Table of Ka for Acids and Bases

A nice demo - watch when doing topic on Acids / Bases and Indicators - second half of video tells you how it was done ! https://www.youtube.com/watch?v=arNyofkuBxM

An Indicator- Phenolphthalein :
http://www.chempage.de/lexi/phenolphth.jpg

Buffer - Diagram of an Acid Buffer
You can create an acid buffer to whatever pH you want, depending on the proportions of salt and acid you add in. And here is how an acid buffer would deal with keeping a steady pH when Hydrochloric acid is added :
Very good explanation of Buffers from Chemguide - to go with my diagram above: http://www.chemguide.co.uk/physical/acidbaseeqia/buffers.html

Working out Logs etc - this might help if you don't know which buttons to press on your calculator to work out logs etc for buffer calculations :

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Delta G Delta S - Entropy - Free Energy in a system / reaction
Visit Website with Explanation

Spontaneous Reactions
ΔG, ΔH and ΔS
http://www.ck12.org/book/CK-12-Chemistry-Intermediate/section/20.2/

Ellingham diagrams
Diagrams plotting delta G vs Temperature for a reaction
https://en.wikipedia.org/wiki/Ellingham_diagram

Reaction Rates - First Order Reactions etc ...
The first three pages of this section are useful, but page 4 I think is not in Adv H Chem and page 5 will become more understandable once you have completed Unit 2 Organic Chemistry :
http://www.pearsonschoolsandfecolleges.co.uk/AssetsLibrary/SECTORS/Secondary/PDFs/Science/EdexcelScience/ALevelRevisionGuides/EdexcelA2ChemistryRG_9781846905964_pg8-17_web.pdf

This is extra - not needed for Adv H - 1st yr Univ or maybe A Level but you might find it of interest -https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/Reaction_Rates/Half-lives_and_Pharmacokinetics

Rate Determining Step and working out Reaction Mechanisms
Very good video ! Listen to all 14 minutes of it - it goes past very quickly and is very clear !
Thanks to excellent Hartlepool Sixth Form College teacher !