Qualitative reactions to organic substances, ions and cations make it possible to determine the presence of various compounds using available, in most cases, simple methods. They can be carried out using indicators, hydroxides, oxides. A science that studies the properties and structure of various substances is called "chemistry." Qualitative reactions are part of the practical section of this science.
Inorganic matter classification
All substances are divided into organic and inorganic. The former belong to such classes of compounds as salts, hydroxides (bases, acids and amphoteric) and oxides, also simple compounds (CI2, I2, H2 and others, consisting of one element) belong here.
Salts consist of a metal cation, as well as an anion of an acid residue. The composition of acid molecules includes H + cations and anions of acid residues. Hydroxides are composed of metal cations and anions in the form of OH- hydroxyl group. The composition of the oxide molecules includes atoms of two chemical elements, one of which is necessarily oxygen. They can be acidic, basic and amphoteric. As their name implies, they are able to form various classes of substances in the process of certain reactions. So, acid oxides form acids when reacting with water, and the main ones form bases. Amphoteric, depending on the conditions, can exhibit the properties of both types of oxides. These include compounds of iron, beryllium, aluminum, tin, chromium, and lead. Their hydroxides are also amphoteric. To determine the presence of a variety of inorganic substances in the solution, qualitative reactions to ions are used.
Variety of organic matter
This group includes chemical compounds whose molecules necessarily include carbon and hydrogen. They can also contain atoms of oxygen, nitrogen, sulfur and many other elements.
They are divided into such main classes: alkanes, alkenes, alkynes, organic acids (nucleic, fatty, saturated, amino acids and others), aldehydes, proteins, fats, carbohydrates. Many qualitative reactions to organic substances are carried out using a variety of hydroxides. Also, reagents such as potassium permanganate, acids, oxides can be used for this.
Qualitative reactions to organic matter
The presence of alkanes is mainly determined by the exclusion method. If you add potassium permanganate, it will not discolor. These substances burn with a light blue flame. Alkenes can be detected by adding bromine water or potassium permanganate. Both of these substances are discolored when interacting with them. The presence of phenol can also be determined by adding a bromine solution. In this case, it will discolor and precipitate. In addition, the presence of this substance can be detected using a solution of iron chloride, which, when interacting with it, will give a violet-brown color. Qualitative reactions to organic substances of the alcohol class consist in adding sodium to them. In this case, hydrogen will be released. The burning of alcohols is accompanied by a light blue flame.
Glycerin can be detected with cuprum hydroxide. In this case, glycerates are formed, which give the solution a cornflower blue color. The presence of aldehydes can be determined using argentum oxide. As a result of this reaction, pure argentum is released, which precipitates.
There is also a qualitative reaction to aldehydes, which is carried out using copper hydroxide. For its implementation, it is necessary to heat the solution. At the same time, he must change color first from blue to yellow, then to red. Proteins can be detected using nitric acid. As a result, a yellow precipitate is formed. If cuprum hydroxide is added, it will be purple. Qualitative reactions to organic substances of the acid class are carried out using litmus or iron chloride. In both cases, the solution changes its color to red. If sodium carbonate is added, carbon dioxide will be released.
Qualitative reactions to cations
With their help, it is possible to determine the presence of any metal ions in a solution. Qualitative reactions to acids are to identify the H + cation, which is part of them. This can be done in two ways: using litmus or methyl orange. The first in an acidic environment changes its color to red, the second to pink.
The cations of lithium, sodium and potassium can be distinguished by their flame. The first burn red, the second yellow, and the third a violet flame. Calcium ions are detected by adding carbonate solutions, resulting in a white precipitate.
Qualitative reactions to anions
The most common of them is the detection of OH-, as a result of which it is possible to find out if bases are present in the solution. This requires indicators. This is phenolphthalein, methyl orange, litmus. The first in such an environment acquires a crimson color, the second yellow, the third blue.