Some Gases

A substance in a form like the air that is neither solid nor liquid is gas. Some gases are Oxygen, hydrogen, and nitrogen. Carbon monoxide is a colorless, odorless, poisonous gas. Certain gases are highly explosive. These factories are releasing toxic gases into the atmosphere.

Carbon dioxide -

General methods of preparation

By burning carbon in an excess air

C +O2 → CO2

By burning organic compounds.

CH4 +2O2   →  CO2 + 2H2O + energy

Laboratory preparation of carbon dioxide

Carbon dioxide is prepared in the laboratory by reacting calcium carbonate with dil. hydrochloric acid.

Chemical Reaction:

CaCO3 + 2HCl     →     CaCl2 + H2O + CO2

First of all, pieces of limestone are taken in Wolfe's bottle and dil. HCl is poured from the thistle funnel. When limestone and HCl come in contact, the reaction occurs and CO2 gas is formed. The formed gas passes through the delivery tube to the gas jar. Since the gas is heavier than air, it is collected by upward displacement of air.

Physical properties of Carbon Dioxide

Carbon dioxide is a colorless & odorless gas. It is soluble in water, ethanol, acetone and has the following properties :

• Melting Point: -55.6 deg C
• Boiling Point: -78.5 deg C
• Density: 1.977

Chemical properties of Carbon Dioxide

• Carbon dioxide is a linear covalent molecule.
• Carbon dioxide is an acidic oxide and reacts with water to give carbonic acid.
• CO2 + H2O ==> H2CO3
• Carbon dioxide reacts with alkalis to give carbonates and bicarbonates.
• CO2 + NaOH ==> NaHCO3 (Sodium BiCarbonate )
• NaHCO3 + NaOH ==> Na2CO3 (Sodium Carbonate) + H2O

Uses of Carbon Dioxide 

1. It is used to neutralize alkaline water.
2. Carbon dioxide is used as an additive to oxygen for medical use as a respiration stimulant
3. Liquid Frozen Carbon Dioxide (Co2) is a good solvent for many organic compounds.
4. Liquid Frozen Carbon Dioxide (Co2) is used as a propellant in aerosol cans, it replaces more environmentally troublesome alternatives
5. It is used for refrigeration and cooling.
6. It is used as an inert gas in chemical processes, in the storage of carbon powder and in fire extinguishers.
7. It is used in solid as well as in the liquid form
8. It is used in the metal industry in the formation of casting moulds to enhance their hardness
9. Carbon dioxide gas is used to carbonated soft drinks, beers and wine and to prevent fungal and bacterial growth.
10. Large quantities are used as a raw material in the chemical process industry, especially for methanol and urea production.
11. It is used in oil wells for oil extraction and maintains pressure within a formation
12. Liquid or solid carbon dioxide is used for quick freezing, surface freezing, chilling and refrigeration in the transport of foods etc.

Ammonia

General methods of preparation

Heating ammonium salts

(NH4)2SO4 2 NH3 + H2SO4

Heating ammonium salts with a strong base

When the mixture of sodium hydroxide and ammonium sulphate is heated, then there is the formation of ammonia gas.
(NH4)2SO4 + 2NaOH → Na2SO4 + 2H2O + NH3

Laboratory preparation of ammonia gas

When a crushed mixture of ammonium chloride is heated with calcium hydroxide, then ammonia produced.

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

For the preparation of ammonia gas, first of all, a mixture of ammonium chloride and slaked lime is taken in a hard glass tube. The test tube is held in a stand-in inclined position. The delivery tube is fixed on the opening of the test tube which is connected to the lime tower. Above the lime tower, the inverted delivery tube is kept. When the mixture is heated, ammonia gas is liberated which passes through the lime tower inside the delivery tube. Since ammonia is lighter than air, it is collected by downward displacement of air.

The test of ammonia gas can be done in the following ways:

1. It changes red litmus into blue.
2. It can be identified by its pungent smell.
3. When it is reacted with HCl, it forms ammonium chloride.

Manufacture of ammonia (Habers synthesis process)

In the industrial sector, ammonia is manufactured at Haber's synthesis process. In this process, nitrogen and hydrogen are heated in the ratio of 1:3 in the presence of iron as catalyst and molybdenum as a promoter at a temperature of about 500oC, under high pressure of about 200 - 900 atmospheric pressure. N2 + 3H2 ↔ 2NH3

It is essential for the production of ammonia in large quantities because it is a reversible process. Since it is reversible, after a certain time product will form the reactants itself, so less reactant is consumed. Along with that, it is an exothermic reaction, so less heat is required.

Uses

I. It is used in the preparation of chemical fertilizers.

II. It is also used for the production of nylons and rayons.