Suppose you have four identical containers with hot solutions. You know it – solutions lithium carbonate, sodium carbonate, potassium carbonate and barium carbonate. Your task is to determine which salt is contained in each tank.
Think of the physical and chemical properties of compounds of these metals. Lithium, sodium, potassium – the alkali metals the first group, their properties are very similar, the activity increases from lithium to potassium. Barium – alkaline earth metal of the second group. Its carbonate salt is highly soluble in hot water but poorly soluble in cold. Stop! That's the first opportunity to determine which container contains barium carbonate.
Cool capacity, such as by placing them in the vessel with ice. Three of the solution will remain transparent, and the fourth will quickly turbid, will begin to precipitate a white precipitate. Here in it and there is the salt of barium. Put the container in the direction.
You can quickly determine barium carbonate. Alternately cast a little of the solution into another container with a solution of any sulphate salt (e.g. sodium sulphate). Only ions of barium, contacting the sulfate-ions, instantly form a dense white precipitate.
So, barium carbonate you have identified. But how do you distinguish salts three alkali metals? It is quite simple to make, you'll need a porcelain Cup for evaporation and a spirit lamp.
Pour a small amount of each solution into a separate porcelain Cup and evaporate the water on the flame of a spirit lamp. Formed small crystals. Put them in the flame of a spirit lamp or a Bunsen burner – with steel tweezers or porcelain spoon. Your task is to notice the color of the outbreak of the "tongue" of flame. If it is a salt of lithium the color will be bright red. The sodium will color the flame a rich yellow color, and potassium in the Magenta-purple. By the way, if likewise experienced a salt of barium flame color should have been green.