Why is sodium kept immersed in kerosene oil?

Explanation :

Sodium is kept immersed in kerosene oil as it is highly reactive and undergoes vigorous reaction as well as accidental fire in open.

Sodium (Na) is a very reactive metal and occupies amongst the top spots in the reactivity series as it is an alkali metal, hence can easily lose an electron to gain it's stable octet configuration. It's high reactivity makes it vulnerable to a very vigorous reaction on contact with surrounding atmosphere, which contains moisture(H₂O) , oxygen(O₂),carbon dioxide (CO₂)etc. It's vigorous reaction could even lead to accidental fire.

Thus, to prevent Na from coming in contact with surrounding atmosphere and it's constituents, it is kept immersed in kerosene oil.

Final Answer :

Hence, sodium(Na) is kept immersed in kerosene oil because it is a highly reactive metal and can lead to vigorous reactions and accidental fire if exposed to H₂O, O₂ etc of atmosphere.Thus  to prevent it from coming in contact with the surrounding atmosphere, it is kept immersed in kerosene which renders it non-reactive.