Question

A metal ‘M’ is stored under kerosene. It vigorously catches fire, if a small piece of this metal is kept open in air. Dissolution of this metal in water releases great amount of energy and the metal catches fire. The solution so formed turns red litmus blue.

1. Name the metal ‘M’.
2. Write formula of the compound formed when this metal is exposed to air.
3. Why is metal ‘M’ stored under kerosene?
4. If oxide of this metal in treated with hydrochloric acid, what would be the products?
5. Write balanced equations for:
   1. Reaction of ‘M’ with air.
   2. Reaction of ‘M’ with water.
   3. Reaction of metal oxide with hydrochloric acid.

Answer 1

1. Name of the metal is sodium (Na).
2. Formula of the compound formed is Na₂O.
3. When exposed to oxygen, metals like potassium and sodium react so quickly that they can ignite. They are constantly submerged in kerosene oil to prevent unintentional fire because they are the most reactive metals.
4. Water and sodium chloride are the products of the reaction between sodium oxide and hydrochloric acid.
5. 1. 4Na + O₂ → 2Na₂O
   2. 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + heat
   3. Na₂O_(s) + 2HCl_(aq) → 2NaCl_(aq) + H₂O_(l)