Qualitative reactions for 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. The science that studies the properties and structure of various substances is called "chemistry". Qualitative reactions are part of the practical section of this science.
Classification of inorganic substances
All substances are divided into organic and inorganic. The former include such classes of compounds as s alts, hydroxides (bases, acids and amphoteric) and oxides, as well as simple compounds (CI2, I2, H2 and others consisting of one element).
S alts consist of a cation of a metal, 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 the OH- hydroxyl group. The composition of 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 course of certain reactions. Thus, acidic oxides react with water to form acids, while basic oxides 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 a solution, qualitative reactions for ions are used.
Diversity of organic matter
This group includes chemical compounds, the molecules of which necessarily include carbon and hydrogen. They may also contain atoms of oxygen, nitrogen, sulfur and many other elements.
They are divided into the following main classes: alkanes, alkenes, alkynes, organic acids (nucleic, fatty, saturated, amino acids and others), aldehydes, proteins, fats, carbohydrates. Many qualitative reactions on organic substances are carried out using a variety of hydroxides. Reagents such as potassium permanganate, acids, oxides can also be used for this.
Qualitative reactions to organic substances
The presence of alkanes is mainly determined by the elimination method. If you add potassium permanganate, it will not discolour. These substances burn with a light blue flame. Alkenes can be detected by adding bromine water or potassium permanganate. Both of these substances become colorless when interacting with them. The presence of phenolcan also be determined by adding a solution of bromine. At the same time, it will discolor and precipitate. In addition, the presence of this substance can be detected using a solution of ferric chloride, which, when interacting with it, will give a violet-brown color. Qualitative reactions to organic substances of the class of alcohols consist in the addition of 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 using 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 should change color first from blue to yellow, then to red. Proteins can be detected using nitrate acid. As a result, a yellow precipitate is formed. If you add cuprum hydroxide, it will be purple. Qualitative reactions to organic substances of the class of acids are carried out using litmus or ferric 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
They can be used to determine the presence of any metal ions in a solution. Qualitative reactions to acids are to identify the cationH +, 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.
Lithium, sodium and potassium cations can be distinguished by their flames. The first burn red, the second - yellow, 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 these is the detection of OH-, as a result of which it is possible to find out whether bases are present in the solution. This requires indicators. These are phenolphthalein, methyl orange, litmus. The first in such an environment becomes crimson, the second - yellow, the third - blue.
