Titrations

Titrations

Acid – Base Titration

•Calculate the concentration of sodium hydroxide using the known concentration of hydrochloric acid.

• 1.Use a pipette to measure 25cm3 of alkali of unknown concentration.

  2.Put the alkali into a conical flask with phenolphthalein indicator. Place the conical flask on a white tile.

  3.Put the acid into the burette. Run a small amount through the tap and then turn off. Take the starting reading of the volume of acid

Carrying Out a Titration

4.Add the acid to the alkali a bit at a time, giving the flask a regular swirl.

5.Watch the colour of the indicator. As it starts to get longer for the colour to reappear, you are getting towards the endpoint of the reaction.

Carrying Out a Titration

4.Add the acid to the alkali a bit at a time, giving the flask a regular swirl.

5.Watch the colour of the indicator. As it starts to get longer for the colour to reappear, you are getting towards the endpoint of the reaction.

6.As you approach the endpoint, start to add the acid drop by drop.

7.Record the volume of acid used to neutralise the alkali.

8.Repeat at least 3 times.

If, for example, your results were:

• 25.0cm3 of sodium hydroxide required 20.0cm3 of 0.100 mol dm-3 hydrochloric acid for neutralisation. 

• What is the concentration of the sodium hydroxide?