Ammonia - Properties, Preparation, Uses, Effects

Ammonia is made up of hydrogen and nitrogen. It is known as ammonium hydroxide in its aqueous form. This inorganic compound has a strong odour. It is dangerous and caustic in its concentrated form. Ammonia has a density of 0.769 kg/m³ at STP, making it lighter than air. It's commonly used as a fertiliser. It's also used in the production of explosives like nitrocellulose and TNT. It is also used in the production of soda ash and the Ostwald process to produce nitric acid.

Ammonia, also known as NH₃ is a colourless gas with the chemical formula NH₃. 

Properties of Ammonia 

1. Since it combines with many acids to form salts, ammonia is known to be a weak base. Ammonia, for example, is converted into ammonium chloride when it reacts with hydrochloric acid. 
2. All salts formed by such acid-base reactions are known to contain ammonium cation, denoted by NH₄⁺. 
3. Ammonia has weak acidic properties and can thus be classified as an amphoteric compound. 
4. Ammonia's acidic properties allow it to form amides with some alkali metals and alkaline earth metals. 
5. When lithium is exposed to liquid ammonia, a similar reaction occurs, resulting in the formation of lithium amide (LiNH₂). 
6. When dissolved in water, the NH3 molecule undergoes self dissociation. The ammonia molecule's molecular autoionization results in the formation of its conjugate base (NH₂^–) and conjugate acid (NH₄⁺). 
7. Because ammonia is a relatively weak base in general, it can be used as a buffer (for the control of pH changes).

Preparation of Ammonia

Ammonia was primarily manufactured until the early 1900s by dry distilling animal waste products and certain nitrogen-rich vegetable waste. The distillation of these waste products reduced nitrites and nitrous acids as well as hydrogen. Ammonia was eventually obtained as a product. Ammonia is now produced industrially using the Haber-Bosch process, which involves a gaseous phase reaction between molecular nitrogen and molecular hydrogen. It should be noted that this reaction occurs at relatively high temperatures and pressures.

• Ammonia is found in trace amounts in the atmosphere and soil, where it is formed by the decay of nitrogenous organic matter such as urea.

NH₂CONH₂ + 2H₂O  ⇢  (NH₄)₂CO₃  ⇌  2NH₃ + H₂O + CO₂

• In the laboratory, ammonia is easily produced by heating an ammonium salt, such as ammonium chloride NH₄Cl, with a strong alkali, such as sodium hydroxide or calcium hydroxide.

2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2H₂O + 2NH₃(g)

Warming concentrated ammonium hydroxide can also produce gas.

Uses of Ammonia 

1. It is used as fertiliser because it increases crop yield.
2. It is used as a cleaner in the home – NH₃ is mixed with water to clean stainless steel and glass.
3. It is used as an antimicrobial agent in food products.
4. It is used in the fermentation process.
5. It is employed as a refrigerant.
6. It is used in the fermentation process as a pH adjuster.
7. It is used to neutralise pollutants such as nitrogen oxides, which are emitted by diesel engines.
8. It is used as a rocket engine fuel.
9. It is widely used in the textile industry.
10. It is used in the production of synthetic fibres such as rayon and nylon.

Liquid ammonia as a solvent

The most studied and well-known non-aqueous ionising solvent is liquid ammonia. The ability of this compound to dissolve alkali metals to form strongly coloured, electrically conductive solutions containing solved electrons is its most notable property. Apart from these notable solutions, much of the chemistry of liquid ammonia can be described using aqueous solutions by comparing similar reactions.

Side effects of inhaling ammonia

When large amounts of ammonia are inhaled, the most common symptoms are a burning sensation in the throat, nose, and respiratory tract. This can eventually lead to respiratory distress or respiratory failure. When the ammonia concentration in the atmosphere is low, the most common side effects are throat irritation and nose irritation.

Ecological Effects of Ammonia

Ammonia will harm aquatic life even at extremely low concentrations. Ammonia is a naturally occurring substance in the environment. When lightning strikes and rain falls on the earth, a small amount of ammonia is produced. However, microbes in water and soil produce the largest majority of ammonia as a byproduct of plant and animal waste decomposition. It can be found in relatively low nontoxic concentrations in soil, air, and water and serves as a nitrogen source for plants. Ammonia undergoes numerous complex biochemical transformations in soils and water. These transformations are collectively referred to as the nitrogen cycle.

1. Ammonia in Water: Ammonium and hydroxide ions are formed when water reacts with ammonia. Ammonia is also known as unionised ammonia. Ammonia is toxic to aquatic organisms, whereas ammonium is not. In water, an equilibrium exists between toxic ammonia and non-toxic ammonium.
2. Ammonia in Air and Soil: Following an ammonia discharge, the vapours evaporate and combine with moisture in the air to create ammonium, which finally falls to earth as rain. The ammonium then quickly binds to the negatively charged organic matter and clays in the soil. Because bacteria quickly convert ammonium that is not taken up by plant roots into nitrates, ammonium rarely accumulates in soil (nitrification). Nitrates can be absorbed by roots or leached through the soil profile. Because ammonium is soil bound, unless washed away by rainfall events, the contamination will likely remain horizontally but leach vertically as nitrates through the root zone.
3. Ammonia Affecting Plants: Water is the primary component of plants, trees, and crops. If there is a large ammonia release, the vapour will most likely burn the leaves of nearby downwind vegetation. Ammonia draws water from the leaves but has no effect on the roots, so damaged plants will most likely recover completely, though affected crops may experience yield loss.

Sample Questions

Question 1: What is liquor ammonia?

Answer:

Liquor ammonia is a very concentrated ammonia solution in water. It may be used to make ammonia by boiling it. The ammonia generated when ammoniacal liquor is cooked with milk of lime is passed through ice or cold water to form liquor ammonia.

Question 2: What is the difference between liquor ammonia and liquid ammonia?

Answer:

Ammonia condenses into a colourless liquid that boils at – 33.4°C when cooled under pressure. This is liquid ammonia that, when cooled further, solidifies into a white crystalline snow-like solid that melts at –77.7°C. Because the heat of vaporization of liquid ammonia is 5700 calories per gram molecule, it is employed as a refrigerant. Liquid ammonia is a liquefied form of ammonia that comes in cylinders.

Question 3: Explain why ammonium nitrate is not used in the preparation of ammonia.

Answer:

Because ammonium nitrate is explosive in nature and dissociates into nitrous oxide and water when heated, it is not employed in the production of ammonia.

Question 4: Which feature of the Ammonia molecules leads to the formation of the Ammonium ion when Ammonia dissolves in water. Name the other ion formed when Ammonia dissolves in water.

Answer:

On the nitrogen atom of an ammonia molecule, one lone pair of electrons is available. The creation of ammonium ion is caused by this lone pair of electrons.

Question 5: What are the products formed when ammonia is oxidised with copper oxide?

Answer:

Nitrogen, copper and water.