Compounds of Carbon

Carbon has a variable valency of 2 and 4

two important kinds of oxides namely carbon monoxide and carbon dioxide.

Both these oxides are gases at room temperature.

Carbon Dioxide - Occurrence

an Baptista van Helmont discovered the presence of carbon dioxide in the year 1630.

It is added to the air by the following processes:a) Respiration of all animals and plantsb) Combustion of carbonaceous fuelsc) Decay of organic matterd) Fermentatione) As a result of volcanic eruptions.In the form of compounds, it is present as

carbonate and bicarbonate salts.

Carbon cycleThe cyclic changes that carbon undergoes in nature is referred to as the Carbon cycle.

Formation of Carbon Dioxide

on burning wood, the main products obtained are carbon dioxide and water vapours.

Laboratory Preparation of Carbon Dioxide

Remember :Dilute sulphuric acid should not be used in

this preparation as it forms a white insoluble layer of calcium sulphate around the marble chips. This coating does not allow the marble chips to come in contact with the acid. As result, the reaction stops.

Tests for Carbon Dioxide

Carbon dioxide is a colourless and almost tasteless gas that puts off a flame.

It turns blue litmus paper red.turns limewater milky. In carbon dioxide, a burning magnesium

ribbon continues to burn .

Physical Properties of Carbon Dioxide

Carbon dioxide is a colourless, odourless gas very slightly sour in taste.

Density :carbon dioxide is heavier than air. Its vapour density is 22 (Vapour density of air = 14.4).

Solubility:It is only slightly soluble in water.

Liquefaction:When compressed to 70 atmospheres at room temperature, it liquefies to form liquid carbon dioxide. The liquid carbon dioxide solidifies to form a snow like solid carbon dioxide, commonly called 'Dry ice'.

Chemical Properties of Carbon Dioxide

Carbon dioxide is slightly acidic. It turns blue litmus paper red.

Stability:It is very stable gas at ordinary temperature and pressure.

CombustibilityCarbon dioxide is neither combustible, not a

supporter of combustion. A burning splinter or a burning candle, gets put off , but metals like potassium, sodium, magnesium etc. continue to burn in carbon dioxide.

Reaction with water

Action with basic oxides

Action with alkalis

Action on heated carbon

Uses of Carbon Dioxide

Carbon dioxide is used in photosynthesis by green plants to produce carbohydrates.

To induce natural breathing.To extinguish fires

As a refrigerant:Solid carbon dioxide called "Dry ice" can provide temperatures as low as -109.3o F. It is superior to ordinary ice, for the following reasons

Manufacture of fertilizer

In the baking industry

In medicineA mixture of 97% oxygen and 3% carbon

dioxide, called carbogen is used to revive persons affected by carbon monoxide poisoning, pneumonia, asphyxiation etc.

Manufacture of aerated drinksFood storageIn the entertainment industry