Available Answers

1. 1.

   Fill in the blank spaces by choosing the correct words from the given list :

   List : nine, free hydrogen, cells, Henry Cavendish, magnesium oxide

   1. Hydrogen gas was discovered by ______________ in 1766.
   2. The sun has ______________ as largest constituent.
   3. Every ______________ parts of water by weight contain one part of hydrogen by weight.
   4. Hydrogen is vital constituent of ______________ of plants and animals.
   5. When steam is passed over heated magnesium powder, it forms ______________ and hydrogen gas.
2. 2.

   Statements given below are incorrect. Write the correct statements.

   1. Sodium metal reacts with hot water to form sodium hydroxide and hydrogen gas.
   2. Zinc dissolves in sodium hydroxide to form zinc hydroxide and hydrogen gas.
   3. In laboratory preparation of hydrogen gas, the reactants are aluminium and dilute sulphuric acid.
   4. In laboratory preparation of hydrogen gas ferrous sulphate is used as catalyst.
   5. The acid used to make acidulated water in the electrolysis of water is carbonic acid.
3. 3.

   Match the statements in Column A, with those in Column B.

   Column A	Column B
   1. A metal which floats on the surface of cold water and reacts with it to form hydrogen gas.	(a) Zinc
   2. A metal which sinks in cold water and reacts with it to form hydrogen gas.	(b) Aluminium
   3. A silvery white metal in the form of a ribbon and reacts with steam on heating to form hydrogen.	(c) Sodium
   4. A metal which is used as reactant in the laboratory preparation of hydrogen gas.	(d) Magnesium
   5. A metal which reacts with sodium hydroxide to liberate hydrogen gas.	(e) Calcium

    

4. 4.

   Write 'true' or 'false' in front of following statements :

   1. Magnesium reacts with caustic soda solution to liberate hydrogen gas.
   2. Sodium reacts with hydrochloric acid explosively.
   3. On electrolysis of acidulated water, two volumes of oxygen and one volume of hydrogen are formed.
   4. Zinc sulphate is used as catalyst during laboratory preparation of hydrogen gas.
   5. Calcium reacts with cold water and forms calcium hydroxide and hydrogen gas.
5. 5.

   Tick (√) the most appropriate answer.

   1. The credit of discovery of hydrogen goes to :
      1. Lavoisier
      2. Robert Boyle
      3. Henry Cavendish
      4. Francis Bacon
   2. In free state hydrogen gas is present in :
      1. natural gas
      2. stars
      3. petroleum gas
      4. coal gas
   3. The metal which does not react with dilute sulphuric acid is :
      1. aluminium
      2. zinc
      3. copper
      4. iron
   4. The substance(s) which contain hydrogen in combined state is :
      1. carbohydrates
      2. fats
      3. proteins
      4. all the above.
   5. Red hot iron reacts with steam to form :
      1. ferrous oxide and hydrogen
      2. ferric oxide and hydrogen
      3. magnetic oxide of iron and hydrogen
      4. magnetic oxide of iron and oxygen.
6. 6.

   Name three metals which react with cold water to form hydrogen gas. Support your answer with fully balanced chemical equations.