Page 157 - ICSE Chemistry 8

Activity 7.1

Aim: To show that hydrogen gas is lighter than air
Materials required: Some hydrogen gas, a balance, two glass jars with lidsids

Procedure
• Take two gas jars of equal size and weight.
• One jar contains air. Fill the other jar with equal volume of
hydrogen and place the lid on both the jars.

• Place the two jars with their lids on the pans of a balance. hydrogen
Observa on: The jar containing hydrogen is lighter than the jar air
containing air.

Conclusion: Thus, hydrogen gas is lighter than air.

Activity 7.2

Aim: To show that hydrogen gas is combus ble
Materials required: A glass jar fi lled with hydrogen, a lighted candle
hydrogen gas
Procedure
• Take a gas jar fi lled with hydrogen.
• Invert it over a burning candle as shown in the fi gure.

Observa on: The candle gets ex nguished and the gas burns with a pop
sound.
Conclusion: This shows that hydrogen gas is combus ble.

Chemical Properties of Hydrogen

• Ac on with litmus: Hydrogen is a neutral gas. It is neither acidic nor basic, hence no change occurs
in the colour of litmus.
• Combus bility: Hydrogen is combus ble in air but it does not support combus on. Pure hydrogen
burns in air with a pale blue fl ame producing water vapour and heat energy.

• Reac on with oxygen: The reac on of hydrogen with oxygen is highly exothermic. Hydrogen burns
in oxygen with a pale blue fl ame to form steam which on condensa on forms water. The energy
released in this process is harnessed to propel space rockets.

• Reac on with chlorine: Hydrogen and chlorine combine slowly in diff used sunlight and explosively
in bright sunlight to form hydrogen chloride gas.

H (g) + Cl (g) 2HCl(g) 
2
2
Hydrogen Chlorine Hydrogen chloride

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