4.2 Titration Practical

Topic 4 - Chemical Changes

What is Titration?

an experimental technique used to find an unknown concentration of an acid or an alkali

What is a pipette used for?

used to accurately measure a certain volume of acid or alkali, (normally about 25 cm^3)

What is a conical flask used for?

used to contain the liquid from the pipette

What is the burette used for?

used for adding the acid/alkali into the conical flask

What is the white tile used for?

used to place the conical flask on

Method :

-> Use the pipette to add 25 cm^3 of alkali to a clean conical flask
-> Add a few drops of indicator and put the conical flask on a white tile
-> Fill the burette with acid and note the starting volume
-> Slowly add the acid from the burette to the alkali in the conical flask, swirl to mix
-> Stop adding the acid when the endpoint is reached (when the acid has neutralised the alkali, and the indicator changes colour)
-> Note the final volume reading, and calculate how much acid you added in total
-> Repeat the titration until you get 'concordant results', meaning the volume of the acids are within 0.10 cm^3 of each other
-> Calculate the mean volume of acid needed

Why swirl the conical flask?

to evenly distribute the acid

Why use a white tile?

easier to spot colour change

Colour change : Litmus paper

-> red in acidic solutions
-> blue in alkali solutions

Colour change : Phenolphthalein

-> colourless in acidic solutions
-> pink in alkali solutions

Colour change : Methyl orange

-> red in acidic solutions
-> yellow in alkali solutions