acids and bases Flashcards
pH scale
- goes from 0-14
- acids are 0>7
- alkalis are 7>14
- 7 is neutral
acids
- proton donor
- all acids contain H+ ions
bases
- proton acceptor
- not all bases contain OH- ions
strong vs weak acids and bases
- strong acids and bases fully dissociate
- weak acids and bases partially dissociate
strong acid
low pH high, conductivity (lots of ions)
weak acids
higher pH still below 7, low conductivity (not many ions)
strong alkali
high pH, high conductivity (lots of ions)
weak alkali
lower pH still higher than 7, low conductivity (not many ions)
oxides
- metal oxides are basic/alkali
- non-metal oxides are acidic
- some oxides are amphoteric, neutralises both acids and alkalis
- some oxides are neutral CO, N2O
neutralisation in tritration
H+ ions react with OH- ions and form water
if an alkali is in a conical flask the pH is high as their are many OH- ions, as H+ ions are added the pH slowly drops until the point of neutralisation. when acid is added in excess pH is low
salts from insoluble base
- add excess base to acid
- filter any unreacted base
- heat to evaporate, allowing crystals to form
salts from soluble bases
- use an acid-base titration to find the exact volume of soluble base
- mix these correct proportions which will produce a solution of the salt and water only
- warm solution to evaporate the water, leave to crystallize
precipitation insoluble salts
- mix 2 solutions to form salt
- filter to remove insoluble salt
- wash salt with distilled water
- leave salt to dry on filter paper
if reactants are soluble
titration
if base is insoluble
add excess of it to acid to ensure neutralisation and then remove excess
