Question

Which among the following is inert gas and not very soluble in water too?
A) $O_2$
B) $C{O}_2$
C) $N_2$
D) $H_{2}S{O}_4$
E) $He$

Answer 1

Hint: Group 18 of the periodic table contains inert gases. On moving down the group 18, solubility increases with increase in atomic size due to increase in the intermolecular attraction between inert gas molecules and water molecules.

Complete step by step answer:
An inert gas is a gas that does not undergo any chemical reaction in a given set of conditions. The group 18 elements are considered inert gases and these are: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). The general configuration of their valence shell is $n{s}^{2}n{p}^6$. Their octet is complete and thus they are inert in nature.
Among the given options, only He (helium) belongs to the group 18 and therefore, is an inert gas.
Now comes to the solubility of inert gases in water. All inert gases are sparingly soluble in water but their solubilities differ relatively. The solubility of inert gases in water is due to dipole-induced dipole interaction, which increases with increase of atomic size or mass of inert gases.
As we move down the group, atomic size increases, interaction between gas molecules and water molecules increases because heavier molecules can be easily polarised by the water molecules and thus easily distort their electron cloud. Consequently, due to this reason, the solubility of inert gases increases from He to Rn. Therefore, helium (He) is the least soluble or we can say not very soluble in water.
Thus, option (E) is correct.

Note: Radon (Rn) is the most soluble inert gas in water. Helium is the second most abundant element in nature and it is colourless, odourless and tasteless. Helium is also the least reactive of all the elements. Nowadays, inert gases are also named as noble gases.