A colorless gas with a pungent odor, ammonia NH 3 not only dissolves well in water with heat. The substance actively interacts with H 2 O molecules with the formation of weak alkali. The solution received several names, one of them is ammonia water. The compound has amazing properties, which are the method of formation, composition and chemical reactions.
Ammonium ion formation
The formula for ammonia water is NH
4 OH. In the composition of the substance there is a cation NH
4 + , which is formed by non-metals - nitrogen and hydrogen. N atoms in the ammonia molecule use only 3 of 5 external electrons to form
covalent polar bonds , and one pair remains unclaimed. In a strongly polarized water molecule, H
+ hydrogen protons are weakly bound to oxygen, one of them becomes a donor of a free electron nitrogen pair (acceptor).
An ammonium ion is formed with one positive charge and a special type of weak covalent bond — the donor – acceptor bond. In its size, charge and some other features, it resembles a potassium cation and behaves like alkali metals. An unusual chemical compound reacts with acids to form salts of practical importance. Names that reflect the characteristics of the preparation and properties of the substance:
- ammonia water;
- ammonium hydroxide;
- ammonia hydrate;
- caustic ammonium.
Precautions
Care must be taken when working with ammonia and its derivatives. Important to remember:
- Ammonia water has an unpleasant odor. The released gas irritates the mucous surface of the nasal cavity, eyes, causes a cough.
- When storing ammonia in loose containers, ampoules, ammonia is released.
- It can be detected without instruments, only by smell even a small amount of gas in solution and air.
- The ratio between molecules and cations in solution changes at different pH.
- With a value of about 7, the concentration of toxic gas NH 3 decreases, the amount of NH 4 + cations less harmful to living organisms increases
Obtaining ammonium hydroxide. Physical properties
When ammonia dissolves in water, ammonia water is formed. The formula of this substance is NH 4 OH, but in fact ions are simultaneously present
NH 4 + , OH - , molecules of NH 3 and H 2 O. In the chemical reaction of ion exchange between ammonia and water, an equilibrium state is established. The process can be reflected using a diagram in which oppositely directed arrows indicate the reversibility of the phenomena.
In the laboratory, the production of ammonia water is carried out in experiments with nitrogen-containing substances. When ammonia is mixed with water, a clear, colorless liquid is obtained. At high pressures, the solubility of the gas increases. Water gives more ammonia dissolved in it with increasing temperature. For industrial needs and agriculture on an industrial scale receive 25 percent substance by dissolving ammonia. The second method involves the use of a reaction of coke oven gas with water.
Chemical properties of ammonium hydroxide
Upon contact, two liquids - ammonia water and hydrochloric acid - become covered with puffs of white smoke. It consists of particles of the reaction product - ammonium chloride. With a volatile substance such as hydrochloric acid, the reaction occurs directly in the air.
Weakly alkaline chemical properties of ammonia hydrate:
- The substance reversibly dissociates in water to form an ammonium cation and a hydroxide ion.
- In the presence of an NH 4 + ion, a colorless phenolphthalein solution turns a crimson color, as in alkalis.
- The chemical reaction of neutralization with acids leads to the formation of ammonium salts and water: NH 4 OH + HCl = NH 4 Cl + H 2 O.
- Ammonia water undergoes ion exchange reactions with metal salts, which correspond to weak bases, and water-insoluble hydroxide is formed: 2NH 4 OH + CuCl 2 = 2NH 4 Cl + Cu (OH) 2 (blue precipitate) .
Ammonia water: application in various sectors of the economy
An unusual substance is widely used in everyday life, agriculture, medicine, industry. Technical ammonia hydrate is used in agriculture, the production of soda ash, dyes and other types of products. In liquid fertilizer, nitrogen is contained in a form easily digestible by plants. The substance is considered the cheapest and most effective for application in the pre-sowing period for all crops.
Three times less money is spent on the production of ammonia water than on the production of solid granular nitrogen fertilizers. For storage and transportation of liquids, hermetically sealed steel tanks are used. Some types of dyes and hair bleaches are made using caustic ammonium. In every medical institution there are drugs with ammonia - a 10 percent solution of ammonia.
Ammonium salts: properties and practical significance
Substances that are obtained by the interaction of ammonium hydroxide with acids are used in economic activities. Salts decompose upon heating, dissolve in water, and undergo hydrolysis. They enter into chemical reactions with alkalis and other substances. Chlorides, nitrates, sulfates, phosphates and ammonium carbonates have acquired the most important practical importance .
It is very important to follow the rules and safety measures when working with substances that contain ammonium ion. When stored in warehouses of industrial and agricultural enterprises, in subsidiary farms there should be no contact of such compounds with lime and alkalis. If the tightness of the packages is broken, a chemical reaction will begin with the release of toxic gas. Everyone who has to work with ammonia water and its salts must know the basics of chemistry. Subject to safety requirements, the substances used will not harm people and the environment.