Question

Metal which is kept immersed in kerosene oil.
A.) Gold
B.) Sodium
C.) Magnesium
D.) Aluminium

Answer 1

The highly reactive metals according to reactivity series are kept immersed in kerosene oil. The metal higher in reactive series reacts with the Oxygen, Carbon dioxide ($CO_2$) and moisture present in the air and may cause fire. In order to prevent these metals from accidental fire, they are kept immersed in kerosene.

Complete answer:
The metals such as sodium, potassium are highly reactive in nature due to its tendency to release valence electrons very easily. Sodium has one electron in its outermost shell and thus wants to give up one electron to the most electronegative element. They do not exist freely and are always found in compound form. When exposed in the atmosphere sodium reacts vigorously with the oxygen ($O_2$) present in the air and forms sodium oxide (${{Na_2}O}$).

$4Na + O_2 \to 2Na_2O$

Sodium is also not kept in water because it reacts violently with water. Sodium gives the outermost electron to $H^+$ ions present in water and a redox reaction takes place between $H^+$ and Na to give $H_2$. This is an exothermic reaction.

$2Na + 2H_2O \to 2NaOH + H_2$

The hydrogen gas which is produced in this exothermic process reacts strongly with the oxygen ($O_2$) present in the air.
The remaining metals such as aluminium, magnesium and gold are less reactive so they do not catch fire when exposed in the atmosphere. These metals either exist freely or in the compound form. Gold is not reactive in nature so it is found at the bottom of the reactivity series. It is also called noble metal.

So the correct option is B.)

Note: While solving this type of question one be aware about the facts related to the elements and the nature of the element and one should know that potassium is also kept in kerosene some time option may be potassium .