Purpose: To become familiar with the methods of separating substances from one another using decantation, extraction, and sublimation techniques.
Apparatis and Chemicals: balance, Bunsen burner, rubber hose, tongs, 2 evaporating dishes, 2 watch glasses, 100-mL graduated cylinder, clay triangles, 2 ring stands, 2 iron rings, 2 glass stirring rods, unknown mixture of NaCl, NH4Cl, SiO2.
Discussion: Mixtures are composed of two or more substances mixed together. Mixtures can be homogeneous, or uniformly distributed; they can also be heterogeneous, or not uniformly distributed. The components of a mixture remain chemically unchanged. They are merely physically mixed. Therefore, it is possible …show more content…
These substances are insoluble in water. Thus, if a soluble substance is mixed with an insoluble substance, separation through decantation can take place. Decantation involves pouring water onto a mixture and stirring. The soluble substance will dissolve, leaving the insoluble one intact. The newly-formed aqueous mixture of water and the soluble substance can be poured into a separate container and heated so that the water evaporates. The substance have now been separated without any changes to the elemental composition of the substances. Decantation is usually performed more than once on the insoluble substance to ensure that all particles of the soluble substance have been removed.
Some substances can pass directly from the solid to the gaseous stage without first melting and becoming liquid. These substances are said to be able to sublime. Substances that sublime, when mixed with substances that do not sublime, can be separated by heating the mixture until the substance that can sublime is completely gone.
Another method of separation is called filtration. This is the process of separating a solid from a liquid by means of a porous filter which allows the liquid to pass through …show more content…
Thus, the mass of the ammonium chloride could never be determined.
Only the mass of sodium chloride and silicon dioxide could be determined.
2. BaSO4 has a very low solubility in water. NH4Cl has a very high solubility in water.
Thus, the mixture could be put in water and decanted. This would separate the two substances.
3. BaCl2 is very soluble in water but CaSO4 is not. So add water. Then filtrated to get the BaSO4. Evaporate the solution and you get back BaCl2.
4. Just add water. The potassium bromide will go into solution, the naphthalene will not. Filter off the naphthalene. Allow the water in the potassium solution to evaporate, and you have now separated the naphthalene and the potassim bromide. Or simply put both into an evaporating dish and heat strongly until allof the naphthalene has sublimed. What remains in the dish will be potassium