Acid-base

• Bronsted-Lowry Acid is a proton donor
• Bronsted-Lowry Base is a proton acceptor
• Lewis Theory Acid is a lone pair acceptor
• Lewis Theory Base is a lone pair donor
• Water not represented in Kw as water concentration is very large compared to dissociated ions and any changes to its values are insignificant so its concentration is regarded as constant
• Buffer is a solution which is able to resist changes in pH when small quantities of acid or alkali are added and when diluted in water
• Acidic buffer= weak acid + its sodium salt, acid acid provides large acid concentration to dissolve into H+ when alkali is added, sodium salt provides large CHCOO- concentration which can react with H+ when acid is added
• Acidic buffer- Alkali added- negative ion added reacts with H+ results in equilibrium shifting right as more acid dissociates to H+ to offset the change
• Acidic buffer- acid added- H+ reacts with negative ion from salt to form acid which only partially dissolves, equilibrium moves left
• Alkaline buffer- acid added- H+ reacts with NH3 to form NH4+, H+ can also react with OH- to produce water, equilibrium shifts right to offset change to produce more OH- ions
• Alkaline buffer- alkali added- OH- ion reacts with NH4+ from salt to produce NH3 and water which only partially dissolves, so equilibrium shifts left
• Adding water doesn't affect pH as it changes the concentration X and HX equally
• concentration refers to the amount of a substance dissolved in a given volume of solution, while strength refers to the degree of ionization or dissociation of an acid or base
• Titration is the is the addition of an acid/base of known concentration to an acid/base of unknown concentration in order to determine the concentration, using an indicator to show when neutralisation has occured
• Good indicator should: have a sharp colour change, end point should also be equivalence point, distinct colour change
• Strong acid- strong base = phenolphthalein
• strong acid- weak base = methyl orange
• strong base- weak acid = phenolphthalein
• methyl orange is red in acid, yellow in alkali changes around 4.5
• phenolphthalein is colourless in acid, red in alkali, changes around 9-10
• Can also achieve an acidic buffer by neutralising half the weak acid with an alkali to form a weak acid/soluble salt mixture
• buffers found in shampoos and detergents