Student Number: 13335535
Lab Partner’s Name: Ifeoma Agu
Demonstrator: Maria
Inorganic Chemistry Experiment 3: The Identification of Unknown Samples
Objectives
The experiments were carried out in order to identify 15 samples, through their physical and chemical properties.
Theory
A precipitation reaction is one which produces an insoluble salt as product. An example would be;
Ca(NO3)2 + H2SO4 = CaSO4 + 2HNO3
The calcium salt is insoluble. Precipitation reactions could be used in this experiment to eliminate compounds while attempting to identify others.
Halides react with AgNO3 to form insoluble halides. These ions form white-yellow precipitates that enable differentiation.
Ag+ + NO3 - + M+ + X- = AgX + MNO3
Precipitates …show more content…
The easiest liquid to identify was Ammonium hydroxide (5), due to its characteristic pungent smell. The solid 7, copper sulphate was also easy to identify due to its blue crystals. Once these was eliminated, the two black powders suspected to be CuO and MnO2 were reacted with the other three liquids. It was expected that whichever combination of liquid and black solid formed a blue solution would be H2SO4 and CuO hence, CuSO4 in solution. On identification of sulphuric acid, the following tests were performed expecting the evolution of carbon dioxide on reaction of the acid with carbonates. Therefore, among the soluble solids, (10) exhibited effervescence and was suspected to be sodium carbonate due to its solubility. The powders and crystals were divided depending on their solubility in deionised water. The two insoluble powders were suspected to be zinc carbonate and aluminium oxide. (6) was identified as zinc carbonate due to evolution of CO2 on addition of sulphuric acid. Among the soluble solids, two (1 and 12) formed precipitates in sulphuric acid. One was expected to be Barium chloride and to react with silver nitrate. Hence, (14) and (13) were reacted with 1 and 12. This led to the identification of 1 as barium chloride and 13 as silver