Laboratory preparation of epsom salt?
Answers
Answer:
Preparation of Epsom Salts ( MgSO4 7H2O )
1. Obtain about 20 mL of dilute(2 mol L-1) sulphuric acid in a 100 mL beaker
2. Take some MgO (crude)** in a film canister. MgO react with acid, but does not dissolve in water.
3. Warm the acid a bit, then slowly, with stirring, add MgO until reaction ceases- an excess of MgO.
Note that there may be some bubbling, as the MgO may contain some
carbonate as CO2 from the air has reacted with the MgO
4. Filter the warm solution, filtrate should be clear & colourless
5. Evaporate the filtrate to half the volume to increase the concentration, possibly in a smaller (50mL) beaker, and allow to cool and wait for crystals to appear.
6. H2SO4 + MgO → MgSO4 + H2O
When the salt crystallises the MgSO4 takes water into its crystal to
forming MgSO4 7H2O – Epsom Salts, long thin crystals.
** Crude MgO can be obtained from Ravensdown Fertiliser works.
(03 3440800)
A 25kg bag costs $45 (or about half that if you have an account)
so this experiment can be done by many pupils at a low cost.