Thursday, 19 February 2015

9.2.1 - Laboratory Activity : Preparation of ammonium sulphate

Laboratory Activity 9.2.1:
Preparation of ammonium sulphate
Aim: To prepare ammonium sulphate

» Ammonium solution 2mol dm-3
» Sulphuric acid 1mol dm-3
» Methyl orange

» Pipette
» Burette
» Conical flask
» Dropper
» Retort stand

(A) Neutralisation titration method
1. 25cm3 of 1.0mol dm-3 sulphuric acid are measured using pipette and a poured into a conical flask.
2. By using a dropper, drop two to three drops of methyl orange into the flask.
3. Ammonium solution is poured into a burette. The initial reading of the burette is recorded.
4. The ammonium solution is titrated slowly into the conical flask.
5. Titration stopped when the solution in the conical flask turned from red to yellow. Burette reading is recorded.

(B) Crystallisation of ammonium sulphate
1. The mixture is poured into evaporation bowl and is heated to increase the rate of evaporation.
2. The mixture is then left to cool as to enable the crystallisation process to take place.
3. The crystals are then filtered out, washed with distilled water and dried by pressing against filter paper.

25cm3 of 1.0mol dm-3 ammonium solution are needed to neutralise 25cm3 of 1.0mol dm-3 sulphuric acid. White substance is obtained.

2 mol of ammonium solution are needed to neutralise 1mol of sulphuric acid. Therefore with the same concentration, 2 volumes of ammonium solution are needed to neutralise 1 volume of sulphuric acid, as presented in the equation below.
2NH3(aq) + H2SO4(aq) → (NH4)2SO4(aq)

The white crystals formed are ammonium sulphate.

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