Chemistry Form Four: Chapter 8 - Application of Precipitation of SaltPrecipitation reaction occur all around us. For example, sometimes the pipes in our homes get clogged because precipitates of magnesium and calcium oxides have deposited themselves within the pipes. This can happen with "hard" water.

Another example is a kidney stone. A kidney stone is nothing more than a precipitate - often of calcium ions (from cheese) and oxalates. It is often suggested that a good way to avoid kidney stones is to drink a lot of water. This helps because the solubility of the precipitate increases with the amount of water - thus avoiding the formation of the kidney stone to begin with.

Various size of kidney stone

Chemistry Form Four: Chapter 8 - Preparation of Insoluble Salt

Insoluble salt can be prepared by using double decomposition reaction or precipitation reaction. A precipitate is a solid that forms out of solution. For an insoluble salt such as SILVER CHLORIDE, you need to find a soluble SILVER compound and a soluble CHLORIDE compound. A good choice for the soluble silver compound is SILVER NITRATE because almost all nitrates are soluble. A good choice for the soluble chloride compound is to use a sodium salt because almost all sodium salts are soluble.The precipitate forms because the solid (AgCl) isinsolublein water.

The remaining sodium nitrate is soluble and so only the silver chloride will be precipitated. Once prepared, collect the salt by filtration and wash the solid. Dry it with a few sheets of filter paper.