Question

Why are sodium and potassium kept in kerosene oil?

Answer 1

Sodium and potassium are reactive metals while kerosene oil is not. Reactivity of sodium and potassium are highest among the alkali metals.

Complete step-by-step answer: Sodium and potassium both belong to the first group of periodic tables. They both have one valence electron in their octet and therefore this single electron is responsible for their reactivity.. Sodium and potassium both are highly reactive metals. They react vigorously with oxygen and moisture. The reactivity of sodium with water can be seen in the following reaction,
$Na(s) + {H_2}O(l) \to NaOH(aq) + \dfrac{1}{2}{H_2}(g)$
When sodium comes in contact with water it runs around on the water surface making a hissing sound violently and then finally it disappears. Hydrogen gas is released and sodium hydroxide is formed in aqueous medium. Sodium hydroxide can rapidly absorb carbon dioxide from air, forming carbon monoxide.
Potassium undergoes the same reaction. It is as reactive as sodium and forms potassium hydroxide. When potassium reacts with water it releases a huge amount of energy. It is so much in amount that it can even ignite the hydrogen gas which is released as a byproduct.
If sodium is kept in open it can react with oxygen and can catch fire. Kerosene is a part obtained from distillation of petroleum. It is used to store reactive alkali metals like sodium and potassium because it is inert and does not react with sodium and potassium.
Since potassium and sodium are highly reactive that is why they are kept in kerosene oil so that they cannot react with oxygen and moisture in the atmosphere.

Note: As shown potassium reacts more violently than sodium it is because it comes in a period below sodium atom. Thus it has eight more electrons thus it is easier to remove the outermost electron with less energy and thus it is more reactive.