Question

Assertion
Sodium metal reacts with the oxygen of the air at room temperature to form sodium oxide.
Reason
Metal forms an oxide on exposure to air.
A.Both the assertion and reason are correct and reason is the correct explanation for assertion.
B.Both the assertion and reason are correct but reason is not the correct explanation for assertion.
C.Assertion is correct but reason is incorrect
D.Both assertion and reason are incorrect.

Answer 1

Hint: We need to know that sodium is a silvery-white metal, its atomic number is $11$ and it is highly reactive metal. It is placed in group $1$ . Sodium symbol is $Na$ , it is comes from Latin and sodium get its name from English word Soda. It is the sixth abundant element and it exists in the form of minerals such as rock salt, soda lite and feldspars.

Complete answer:
-We must remember that sodium is a highly reactive metal and it forms sodium oxide (grayish white) when it combines in the air at room temperature.
-Now we can write the chemical equation for this chemical reaction as,
$4Na + {O_2} \to 2N{a_2}O$
-The product formed in the above reaction is unstable; sodium oxide is a strong base because it contains ${O^{2 - }}$ and very soon it forms sodium hydroxide, combined with hydrogen.
-Usually sodium is stored in kerosene, to prevent the reaction with moisture, carbon dioxide and oxygen.
-Metals, when exposed to air, they form oxides.
-From the above points, assertion and reason are correct but reason is not the correct explanation for assertion.
So, Option B. Both the assertion and reason are correct but reason is not the correct explanation for assertion, is the correct answer.

Note:
We need to know that the sodium is a reducing agent. And sodium reacts with air; to prevent this, store sodium in kerosene because in kerosene the compounds are already reduced and there is no further reduction taking place for sodium metal. Sodium loses its outermost electron and thus forms a positive ion. Sodium is an essential mineral for humans. Sodium regulates blood pressure and volume, osmotic equilibrium and $pH$ . In extracellular fluids, sodium cation is a major cation of animals and human beings.