Using Titrations to Find Concentrations:
Titrations allow you to find out exactly how much acid is needed to neutralise a base or vice versa.
- Using a pipette, add 25cm3 alkali to a conical flask along with a few drops of indicator (for alkali, phenolphthalein is good because it makes a drastic change when it is neutral).
- Next, fill a burette with acid and then add the acid to the base drop by drop.
- When the solution changes from bright pink to colourless, you should be able to read off the burette exactly how much acid is needed to neutralise the base.
Working out the Number of Moles:
- Use ths calculation triangle to work out the number of moles.
Step 1 ---> Work out how many moles of the 'known substance' (in the burette) you have.
- Moles = concentration x volume
Step 2 ---> Write down the equation and use this to work out how many moles of the 'unknown substance' you have.
Step 3 ---> Work out the comcentration of the 'unknown substance'
- Concentration = moles / volume