OCR A2 Chemistry : Acids and Bases


Includes definitions, pH, Ka, Kw and buffers
Sarah H-V
Flashcards by Sarah H-V, updated more than 1 year ago
Sarah H-V
Created by Sarah H-V about 9 years ago

Resource summary

Question Answer
equation for pH - log [H+]
How to work out [H+] from pH 10 ^ -pH
Bronsted - Lowry Acid Definition A proton donor
Bronsted - Lowry Base Definition A proton acceptor
Strong Acid Definition An acid which completely dissociates in aqueous solution
Weak Acid Definition An acid which only partially dissociates in aqueous solution
Ka (Acid Dissociation Constant)
Units for Ka mol dm ^ -3
A large Ka indicates what? A large extent of dissociation, therefore the acid is strong
A small Ka indicates what? A small extent of dissociation, therefore the acid is weak
equation for pKa
How to work out Ka from pKa 10 ^ -pKa
The smaller the value of pKa ... ... the stronger the acid
equation for Kw (ionic product of water) [H+] x [OH-]
At 25 degree Celsius, the value of Kw is 1.00 x 10 ^ -14
Units for Kw mol ^ 2 dm ^ -3
Buffer Definition A mixture which minimises pH changes on the addition of small amounts of acid or base
What is an acidic buffer solution made of? A weak acid and a salt of the weak acid e.g ethanoic acid and sodium ethanoate
What is an alkaline buffer solution made of? A weak base and a salt of the weak base e.g ammonia and ammonium chloride
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