Everyone who visited school lessons of chemistry faced high-quality reactions to cations of metals. Definition of cations of metals in the solutions given by the teacher will become one of tasks of test work after passing of material. So, how to learn an aluminum cation?
It is required to you
- - table of solubility;
- - alkali;
- - test tube;
- - filter paper;
- - alizarine;
- - ammonia.
Instruction
1. To find a metal cation, it is necessary to carry out reaction which result will be swept up by a naked eye. Tell such indicators as loss of a deposit, liberation of gas, change of color of substance about successful course of reaction. Knowing what color solution or a deposit at you has to turn out, you without problems will find presence of required metal.
2. Use the table of solubility. In a vertical column anions of salts, and in horizontal – cations of metals are specified. When crossing lines of substances you will see the letters "r", "n", "m" or a crossed out section. "р" designates that this acid with this metal forms soluble salt, "m" - slightly soluble (liquid will be muddy, the suspension or an instant deposit can be formed), "N" - insoluble. If there is a crossed out section, so this salt does not exist.
3. To prove that salt contains an aluminum cation, find an element in a horizontal column and look with what substances it forms a deposit. Follows from the table of solubility that hydroxide of Al (OH) 3 aluminum is slightly soluble, so, reaction during which you receive this substance will serve as the proof of presence of metal.
4. From a flask in a test tube pour a small amount of salt of aluminum. Add several drops of alkali there (NaOH will approach or KOH – their salts are always soluble in water). Reaction will happen instantly, and you immediately will see that solution became transparent-white. At further addition of alkali, liquid will become transparent again. It occurs because aluminum – amphoteric metal, and is capable to form salts with other metals, acting as a part of anion.
5. Write down the reaction equation which will be considered as the proof: Al (salt) 3 + NaOH-> Al(OH)3 + 3Na (salt).
6. It is possible to find aluminum also in the drop way. Apply a small amount of salt on filter paper, previously having moistened it with alizarine solution, and take over the container with the concentrated ammonia solution. If at salt there is an aluminum, the spot will become red color.