2.f - Acids, Alkalis and Titrations Flashcards
what does the pH scale tell you
how acidic or alkaline a solution is
what does the pH scale range from
0-14
0 = strongest acid 14 = strongest alkali
what does a pH of 0-3 mean
strongly acidic
what is the pH of something weakly acidic
4-6
what does neutral substance (eg.water ) have a pH of
7
what does a pH of 8-10 mean
weakly alkaline
what is the pH of something strongly alkaline
11-14
what colours does pH range from ( in terms of universal indicator
Red to Purple (colours of rainbow )
red= strongest acid green = neutral purple = strongly alkaline
what colours for blue litmus paper in acid and alkali
blue litmus = acidic = red
blue litmus = alkali = blue
blue litmus = neutral = blue
what are the colours for red litmus paper
red litmus = alkali = blue
red litmus = acidic = red
red litmus = neutral = red
what are the colours for neutral litmus paper
acidic = red alkali = blue neutral = purple
what colours for phenolphthalein in acid and alkali
acidic = colourless alkali = bright pink
what colours for methyl orange in acid and alkali
acidic = red alkali = yellow
what are acids in aqueous solution a source of
hydrogen ions = H+ ions
what are alkalis in aqueous solution a source of
hydroxide ions = OH- ions
what is the name of reaction between acid + alkali
neutralisation reaction ( acid- base reaction )
what do titrations do
allow you to find out exactly how much acid is need to neutralise an alkali ( or vice versa )
PAPER 2
describe how to carry out an acid- alkali titration
- using pipette add (25cm3) alkali ( sodium hydroxide ) to a conical flask
- add 2 to 3 drops of indicator eg phenolphthalein / methyl orange
- fill a burette with acid
- using burette add acid to alkali a bit at a time - giving conical flask regular swirl ( go really slow when think near colour change )
- indicator changes colour when all alkali has be neutralised ( in this case pink -> colourless )
- record volume of acid used to neutralise the alkali
- repeat + take average