Question

When a small piece of dry sodium is put in water, it reacts vigorously to produce:
(A) Nitrogen gas
(B) Hydrogen gas
(C) Carbon dioxide gas
(D) Sulphur dioxide

Answer 1

Hint: Try to recall that sodium is a highly reactive alkali metal and on reaction with water it produces a gas which is the lightest substance known. Now, by using this you can easily find the correct option from the given ones.

Complete step by step solution:

• It is known to you that sodium is a highly reactive metal. That means it has a single electron in its outer shell which is readily lost in reactions, resulting in a much more stable complete outer electron shell.
• When sodium comes in contact with water, hydrogen gas is liberated and sodium hydroxide is generated that dissolved in water. The reaction of sodium with water is as follows: $2Na(s) + 2{H_2}O \to 2NaOH + {H_2}$.
• The reaction is strongly exothermic, and the heat generated ignites the hydrogen gas.
• A small piece of sodium will dance on the surface of water with a hydrogen flame under and around it.
• A large piece of sodium can sink below the surface of the water, releasing a large amount of hydrogen and heat, resulting in a steam explosion that exposes the hydrogen gas to the atmosphere, where it will also likely explode.
  Therefore, from above we can conclude that option B is the correct option to the given question.

Note:

• It should be remembered to you that sodium is kept/ preserved in kerosene so as to avoid its direct contact with the air. This is due to the high reactivity of sodium metal in air.
• Also, you should remember that the solution formed after the reaction of sodium with water is basic in nature due to dissolution of sodium hydroxide in water.