Required practicals

Question 1

Neutralisation - carrying out a titration

Answer 1

1. Measure a known volume of alkali into a conical flask using a volumetric pipette
2. Add a few drops of acid/base indicator to the solution in the conical flask and swirl
3. Rinse a burette with distilled water, and then with some of the acid, allowing some acid to pass through the tap.
4. Pour the acid into the burette
5. Record the reading on the burette. Then open the tap to release a small amount of acid into the flask. Swirl the flask to make sure that the two solutions are mixed
6. Keep on repeating step 4 until the indicator in the flask changes colour. This shows when the alkali in the flask has completely reacted with the acid added from the burette. Record the reading on the burette and work out the volume of acid that has run into the flask
7. Repeat the whole process at least three times. Discard any anomalous results (usually the first rough titre) Alternatively, keep repeating the titration until you get two results within 0.1 cm^3 of each other (concordant). Calculate the mean value.

Question 2

Describe a method to make pure, dry crystals of magnesium sulphate from a metal oxide and a dilute acid

Answer 2

• Use magnesium oxide and sulphuric acid
• Add sulphuric acid to a beaker and heat the acid
• Add magnesium oxide and stir, continuing adding until the magnesium oxide is in excess
• Filter using a filter paper and funnel to remove excess magnesium oxide
• Heat solution in an evaporating basin to crystallisation point
• Leave to crystallise and pat dry with filter paper