Precipitation occurs when two aqueous (soluble solids) solutions are combined and the reaction forms an insoluble solid. When insoluble solids are formed the process is known as a precipitation. An insoluble solid is a solid that cannot dissolve unlike a soluble solid. Therefore only insoluble solids can form precipitates.
In the following experiment six solutions were mixed with each other (groups of twos) in test tubes to test which reaction will result in an insoluble solid. See method for more detail.
It is expected that the following compounds will form precipitates Silver Sulphate, Copper Hydroxide, Copper Iodide, Silver Hydroxide, Silver Iodide, Cobalt Hydroxide and two Silver Chlorides. This was worked out by completing the double displacement reactions and using a table of solubilities. (See appendix one & two)
In any experiment involving chemicals a hard wearing plastic apron, safety glasses and closed in leather shoes should be worn. When working with dangerous chemicals such as the ones used in this experiment extra safety preparation should be used. Silver Nitrate if comes in contact with skin it imbeds in the dermis creating a black pigment. If this occurs in large quantities or for a long period of time this can cause blackening of the eyes, throat and nose (if breathed in). When working with Silver Nitrate gloves were used to avoid any skin contact. All chemicals were collected in a beaker at the end of the practical and given to an adult to dispose of properly. Method: 1. Following the table, 10 drops of Copper Sulphate were placed in each test tube (five test tubes). 2. 10 drops of Sodium Chloride was added to the first test tube, 10 drops of Silver Nitrate to the second, and so on until each test tube contained Copper Sulphate and one other chemical. 3. Each reaction was recorded and written in the table. (see appendix one for table) 4. The waste was tipped into a beaker to safely dispose of later