Question

Sodium peroxide which is yellow solid, when exposed to air becomes white due to formation of:
(A) ${{H}_{2}}{{O}_{2}}$
(B) $N{{a}_{2}}O$
(C) $N{{a}_{2}}O$ and ${{O}_{2}}$
(D) $NaOH$ and $N{{a}_{2}}C{{O}_{3}}$

Answer 1

Hint: Try to recall that sodium reacts with the oxygen in the air to form sodium oxide and sodium oxide reacts with moisture and carbon dioxide to release oxygen gas. Now, by using this you can easily find the correct option from the given ones.

Complete step by step solution:
-We know that sodium is found in nature in combination with other elements. It’s the seventh element for their abundance in the earth crust and is an essential component of plants and animals.
-It is a metal with the silvery appearance and is very soft, highly reactive and when it is exposed to air is easily oxidized.
-When sodium is exposed to air, it is oxidised to sodium peroxide which is yellow solid by atmospheric oxygen. The reaction is as follows:
\[2Na+{{O}_{2}}\to N{{a}_{2}}{{O}_{2}}\]
-The sodium peroxide then, absorbs water vapour (moisture) from air to form sodium hydroxide which is white in colour, deliquescent in nature and hydrogen peroxide. The reaction is as follows:
\[N{{a}_{2}}{{O}_{2}}+{{H}_{2}}O\to 2NaOH+{{H}_{2}}{{O}_{2}}\]
-Afterwards, the sodium hydroxide absorbs carbon dioxide to form sodium carbonate which is a white coloured solid. The reaction is as follows:
\[2NaOH+C{{O}_{2}}\to N{{a}_{2}}C{{O}_{3}}+{{H}_{2}}O\]
All these happen when sodium is exposed to air for a long time.

Therefore, from above we can easily conclude that option D is the correct option to the given question.

Note: Note that sodium peroxide is a white solid which is used as a bleaching agent, disinfectant and in the production of other chemicals. Also, you should remember that sodium does not form superoxide on reaction with oxygen because superoxide anion is large, so sodium which is a small cation could not stabilize it.