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Salt Preparation

A salt consists of a positive ion (cation) and a negative ion (anion). To prepare a salt, a pair of reagents are required. The reagents to be used will be dependent on whether the salt is soluble or insoluble in water; use the solubility table in the attached file to determine solubility. Group 1 and Ammonium salts (Soluble salts)

This category of salts is soluble in water and their reagents are both soluble. Thus, only titration can be used. The pair of reagents can be (i): acid + alkali or (ii): Metal carbonate + acid Example: To prepare sodium chloride, use sodium hydroxide and hydrochloric acid or use sodium carbonate and hydrochloric acid. Soluble salts except for those that falls into the above category (Soluble Salts) This category of salts is easier to prepare. It involves adding an excess reagent which is in solid state with an aqueous reagent which is limiting. As the product formed is soluble, it can be obtained by filtering out the excess solid reagent. The pair of reagents can be (i): Excess metal + acid (copper cannot be used as it does not react with acid) (ii): Excess metal carbonate + acid (iii): Excess metal oxide + acid Example: To prepare magnesium chloride, use excess magnesium and hydrochloric acid or excess magnesium carbonate and hydrochloric acid or excess magnesium oxide and hydrochloric acid. Insoluble salts

For insoluble salts, the precipitation method is used. Two aqueous reagents are used and since the salt formed is insoluble, it is easily obtained by filtering the final mixture. Example: To prepare silver chloride, use silver nitrate and sodium chloride. This is a safe combination since all nitrates and group 1 salts are soluble.

Solubility Table
PDF • 397KB

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