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The objective of this experiment was to determine the quantitative amount of sulphate using gravimetric method

January 27, 2019 0 Comment

The objective of this experiment was to determine the quantitative amount of sulphate using gravimetric method. The amount of sulphate was measured by in percentage yield, which obtained, 43.15%.
The sodium sulphate solution was digested to break the bonds in the solution in order to make the sulphate in the solution free to precipitate with the BaCl2 to form BaSO4. The barium sulphate precipitate was washed with warm distilled water to free the Cl- ion in the precipitate. Drop of AgNO3 was added, if AgCl precipitate is formed, it indicates that BaSO4 precipitate needs further washing. Next, the precipitate and filter paper was heated until its weight became constant. Heating process removed all the solvent, adsorbed electrolytes and any volatile species that was carried down with the precipitate.
The low results obtained may cause from the excess amounts of mineral acid present. Secondly, coprecipitation of sulphuric acid. This is a source of error in a gravimetric determination of sulphate but not of barium, since this H2SO4 is driven off during ignition. The other factor is coprecipitation of ammonium ion, (NH4)2SO4, which is volatilized upon ignition of the precipitate and partial reduction of BaSO4 to BaS when filter paper charred too rapidly.
To avoid the possible errors, the container that contained BaSO4 was washed with warm water to remove the Cl- salt present. The filter paper and the precipitate were well dried to ensure accurate weight measurement and the experiment was carried out at a near boiling point temperature to increase the solubility of the precipitate at equilibrium and reduce relative super saturation.

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