Page 162 - ICSE Chemistry 8

Quick Review

• Hydrogen is the simplest and the lightest of all the elements.
• Hydrogen makes up almost 90% of the ma er in the universe. It makes only 1.0% of the earth’s crust,
oceans and atmosphere.
• An atom of hydrogen consists of one proton around which one electron revolves.
• Hydrogen combines with other elements to form water, acids, bases, hydrocarbons, carbohydrates,
proteins and fats.
• In 1766, Henry Cavendish discovered the element hydrogen.
• Hydrogen gets displaced from water, acids and alkalis by metals placed above it in the ac vity series.
• Hydrogen is prepared by the ac on of water on metals, dilute acids on metals, alkalis on metals and by
the electrolysis of water.
• In the laboratory, hydrogen is prepared by the ac on of dilute sulphuric acid or dilute hydrochloric acid
on zinc granules.
• Hydrogen is combus ble in air but it does not support combus on.
• Pure hydrogen burns with a pale blue fl ame in air. But impure hydrogen burns in air with a characteris c
pop sound.
• Hydrogen is used in the produc on of ammonia, hydrochloric acid, methanol, ammonia, etc. and for
other purposes.
• Hydrogen is seen as a future source of energy.

EXERCISES

BE PROMPT

A. Fill in the blanks.

1. The most important compound of hydrogen is ____________.
2. ____________ process is used to produce hydrogen on a large scale.

3. Water gas is a mixture of _____________________ and _____________.
4. The reac on of hydrogen with oxygen is highly _____________.
5. Hydrogen combines with carbon to form compounds called _____________.

6. Pure hydrogen burns with a _____________ fl ame in air.

B. Iden fy the error in the given statements. Circle the incorrect word and write the correct word in
the blank.
1. Acidulated water is made by adding a few drops of hydrochloric acid
to make it a be er conductor of electricity. _________________

2. Hydrogen is a basic gas. _________________
3. Hydrogen is used extensively in the produc on of hydrogen carbonate by
Haber’s process. _________________

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