Page 211 - ICSE Chemistry 8

carbon cycle. It is formed during the combus on of hydrocarbon fuels and is also produced in respira on.
Plants use the atmospheric carbon dioxide to prepare food during the process of photosynthesis.
Jan Bap sta van Helmont discovered carbon dioxide gas. Joseph Black showed that limestone cons tutes
of carbon dioxide. The role of carbon dioxide in respira on was studied by Antoine Lavoisier.

Preparation of Carbon Dioxide

Carbon dioxide can be prepared in the following ways.
• By the reac on of dilute acids with metal carbonates

• By burning carbon
• By hea ng metal carbonates or metal hydrogen carbonates

By the Reaction of Dilute Acids with Metal Carbonates

Dilute acids such as dilute hydrochloric acid reacts with calcium carbonate to form carbon dioxide.
2HCl + CaCO 3 CaCl 2 + H O + CO 2
2
Hydrochloric acid Calcium carbonate Calcium chloride Water Carbon dioxide
(dilute)
• A few chips of marble [calcium carbonate (CaCO )] are taken in a Woulfe’s bo le which is a double-
3
mouthed glass bo le with two necks.

• A few drops of dilute hydrochloric acid are added through a thistle funnel.
• An eff ervescence is observed when the acid reacts with marble and carbon dioxide is released.
• Carbon dioxide is heavier than air. It is collected by the upward displacement of air in a glass jar.

dil. HCl
dil. HCl

thistle funnel el

Woulfe’s bottle
ca
carbon dioxiderb
marble chips

Fig. 9.11: Preparation of carbon dioxide in the laboratory
By Burning Carbon

Fuels containing carbon release carbon dioxide on burning.
C + O 2 CO 2 + Heat
Carbon Oxygen Carbon dioxide
Fuel + Oxygen Carbon dioxide + Water vapour + Heat + Light

Wood + Oxygen Carbon dioxide + Water vapour + Heat + Light

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