Page 156 - ICSE Chemistry 8

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CO(g) + H (g) + H O(l) 450 C CO (g) + 2H (g) 
2
2
2
2
Water gas Steam Carbon Hydrogen
dioxide
Step 3: SeparaƟ on of Hydrogen from the Mixture
The mixture is passed through water under approximately 30 atmospheric pressure. Carbon dioxide gets
dissolved in water and hydrogen is collected in cylinders.

The hydrogen that is obtained is refi ned as per the desired levels of purity by other chemical methods.
Carbon dioxide and carbon monoxide can be removed by passing them through aqueous KOH and
ammoniacal CuCl, respec vely.

Take a Break!

Write/Choose the correct answer.

1. The sun is a big ball of hot gases, mainly composed of hydrogen and oxygen. (True/False)

2. An atom of hydrogen consists of one ___________ around which one ___________ revolves.

3. ________________ discovered the element hydrogen.

4. What happens when potassium is treated with cold water?
5. Potassium and sodium do not react violently with cold water. (True/False)

6. When electric current is passed through acidulated water, it dissociates into ___________ and
______________.

7. ______________ process is used to produce hydrogen on a large scale.
8. ______________ is a mixture of carbon monoxide and hydrogen.

PROPERTIES OF HYDROGEN

Let’s study the physical and chemical proper es of hydrogen.

Physical Properties of Hydrogen

• Hydrogen is a colourless, odourless, tasteless and non-poisonous gas.
• It is the lightest of all the gases. One litre of hydrogen gas weighs 0.09 g at 1 atmospheric pressure
and 0°C. It is about 20 mes lighter than air.

3
3
• It is almost insoluble in water. One litre (1000 cm ) of water dissolves about 21.4 cm of hydrogen
gas at ordinary temperature and pressure.
• Hydrogen gas cannot be liquefi ed easily. It liquefi es into a colourless liquid at –240°C and
20 atmospheric pressure.
• The mel ng point of hydrogen is –259°C and its boiling point is –253°C.

• It is a highly infl ammable gas and burns with a pop sound. It has a pale blue fl ame.

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