Chemical changes Flashcards
Definition of an acid
A substance that forms an aqueous solution with a ph of less than 7
Definition of a base
Any substance that will react with an acid to form a salt
Definition of an alkali
A base that dissolves in water to form a solution with a Ph greater than 7
They form OH- ions in water
Definition of titration
A method of analysing the concentrations of solutions
What does a titration allow you to find out
The exact volume of acid needed to neutralise a measured volume of alkali
How do you conduct a titration
- ) Using a pipette or pipette filler add a set volume of alkali to a conical flask. Add two or three drops of indicator as well
- ) Use a funnel to fill a burette with some acid of known concentration. Do this below eye level for safety measures. Record the original volume of acid/alkali in the burette
- ) Use the burette to add the acid to the alkali a bit at the time. Give the conical flask a regular swirl. Go even more slow when you think you are close to neutralisation.
- ) In indicator will change colour when all the alkali has been neutralised
- ) Record final volume of acid in the burette, and use it, along with the initial reading, to calculate the volume of acid used to neutralise the alkali
What colour is phenolphthalein in alkali/acidic solutions
pink in alkaline conditions, but colourless in acidic conditions.
What colour is litmus in acid/alkali solutions
red in acid
blue in alkali
What colour is methyl orange in acid/alkali solutions
red in acids
yellow in alkalis
What is the difference between strong and weak acids?
Strong acids ionise completely in water and all the acid particles dissociate to release H+ ions.
Weak acids partially ionise and dissociate to release H+ ions
Is the ionisation of a weak acid reversible?
Yes
