Properties of ammonia gas

Ammonia is a colorless gas, which has a strong pungent smell (urine smell) and is easily soluble in water. The aqueous solution has strong pungent smell and weak alkalinity. It can be liquefied under normal pressure (critical temperature 132.4℃, critical pressure 1 1.2 MPa, i.e. 1 12.2 atmospheric pressure). Boiling point -33.5℃. It is also easy to be solidified into a snow-like solid. Melting point -77.75℃. Soluble in water, ethanol and ether.

Second, the preparation method

Most industrial ammonia production is made from nitrogen and hydrogen at high pressure, high temperature and in the presence of catalyst. Nitrogen mainly comes from air; Hydrogen mainly comes from synthesis gas containing hydrogen and carbon monoxide (pure hydrogen also comes from electrolysis of water).

The mixed gas consisting of nitrogen and hydrogen is synthetic ammonia feed gas. The feed gas of fuel chemical industry contains sulfur compounds and carbon oxides, which are toxic to the catalyst of ammonia synthesis and need to be purified before ammonia synthesis.

Third, hydrogen bonds between ammonia molecules.

A nitrogen atom has five valence electrons, three of which are unpaired. When it is combined with hydrogen atoms, each nitrogen atom can be combined with three hydrogen atoms through polar valence bonds to synthesize ammonia molecules, and the nitrogen atoms in ammonia molecules also have lone pair. The spatial structure of ammonia molecule is triangular pyramid and polar molecule.

Fourthly, ammonia forms a complex.

Ammonia can react with a solution containing copper (II) ions to form a dark blue complex, and can also be used to prepare analytical chemical reagents such as silver ammonia solution. The main reason is that metal ions provide empty orbits for acids, while ligands provide electrons as bases, and the reaction between transition metals and ligands is often accompanied by color changes.

Extended data

Harm of ammonia gas

Mild ammonia inhalation poisoning is characterized by rhinitis, pharyngitis, sore throat and hoarseness. Ammonia entering trachea and bronchus can cause cough, expectoration and blood in sputum. In severe cases, hemoptysis with pulmonary edema, dyspnea, white or bloody foam sputum, and large and medium-sized blisters on both lungs may occur. The patient has burning throat, cough, expectoration or hemoptysis, chest tightness and retrosternal pain.

The occurrence of acute ammonia inhalation poisoning is mostly caused by accidents such as pipeline rupture and valve burst. Acute ammonia poisoning is mainly manifested as irritation and burns of respiratory mucosa. Its symptoms vary with ammonia concentration, inhalation time and personal sensitivity.

Acute mild poisoning: dry throat, sore throat, hoarseness, cough, expectoration, chest tightness and mild headache, dizziness, fatigue, bronchitis and bronchiolitis.

Acute and moderate poisoning: the above symptoms are aggravated, dyspnea, sometimes bloodshot sputum, mild cyanosis, obvious conjunctival congestion, laryngeal edema, and dry and wet snoring in the lungs.

Acute severe poisoning: severe cough, a lot of pink foam-like sputum, shortness of breath, palpitation, dyspnea, further aggravation of laryngeal edema, obvious cyanosis, or acute respiratory distress syndrome, severe pneumothorax and mediastinal emphysema.

Severe inhalation poisoning: Laryngeal edema, glottic stenosis and respiratory mucosa shedding may occur, which may cause tracheal obstruction and suffocation. Inhalation of high concentration ammonia can directly affect the permeability of pulmonary capillaries, cause pulmonary edema, and induce convulsions, convulsions, drowsiness, coma and other conscious disorders. Individual patients who inhale extremely concentrated ammonia will have respiratory and cardiac arrest.

Reference source: Baidu Encyclopedia-Ammonia