Reducing Action
Ammonia acts as a reducing agent.
a) With Heated Metallic Oxide
When passed over heated metallic oxides, ammonia reduces them to their metals.
Activity
Reducing Action of Ammonia
Place small quantities of copper oxide, lead oxide and iron (III) oxide inside a combustion tube as shown in figure 6.9.
The combustion tube is heated very strongly and then dry ammonia gas is passed through it. Ammonia reduces the metal oxides to their metals.
b) With Chlorine
(i) Excess ammonia with chlorine
When excess ammonia and chlorine are mixed, the chlorine gets reduced to hydrogen chloride.
OR
Activity
Reduction of Chlorine by Ammonia
Set up the apparatus as shown in figure 6.10.
Liquor ammonia is taken in the test tube and boiled. It decomposes to yield ammonia gas and water vapour. The ammonia combines with the chlorine, forming thick white fumes of ammonium chloride.
(ii) Ammonia with excess chlorideIf the chlorine gas is in excess, then the products are nitrogen trichloride, a highly explosive yellow coloured liquid and hydrogen chloride gas.
Action with Carbon Dioxide
a) With Carbon dioxide in the presence of water
When ammonia is treated with a mixture of carbon dioxide and water vapour, it combines to form ammonium carbonate, a colourless, crystalline, highly sublimable salt.
b) With dry Carbon dioxide
When dry ammonia and carbon dioxide are heated to 150oC under a pressure of 150 atmospheres, the two gases combine to form carbamide or urea, and water.
Urea finds use as a nitrogenous fertilizer.
With aqueous solutions of salts
When ammonia is passed through aqueous solutions of certain salts, the respective metallic hydroxides are precipitated.
Physiological action of ammonia
Ammonia affects the lachrymal glands, and brings tears into the eyes. When inhaled it stimulates the muscles of the heart. So it is used to revive people who have fainted. But in large doses, it makes the heart to beat so fast that is becomes fatal.
The properties of ammonia are summarized in figure 6.11 shown below.
