Question

The mixture of noble gases can be separated by
(A) Ramsay-Rayleigh method
(B) Fischer-Ringes method
(C) Dewars adsorption on activated coconut charcoal method
(D) Bartlett method

Answer 1

Hint: Noble gases are also known as inert gases. They are called so because they are chemically inert at ordinary conditions. The inactive nature is due to the completely filled shells in such elements. Their reactions are very less known.

Complete step-by-step answer:
Noble gases are also called as rare gases or inert gases. They are placed in the p-block in group $18$ of the periodic table.
There are six elements in the noble gas group. These are helium, neon, argon, krypton, xenon and radon. All the elements except radon occur in the atmosphere. Radon is obtained as the decay product of ${}^{226}Ra$.
The mixture of noble gases can be separated by Dewar’s adsorption on coconut charcoal method.
This method is based on the fact that activated coconut charcoal adsorbs different gases at different temperatures. The mixture of noble gases obtained from the atmosphere is taken in a bulb filled with activated coconut charcoal and placed in a cold bath. The gases are allowed to remain in the bulb for half an hour and unadsorbed gases are removed and kept separately.
At $-{100}^{o}C$ , coconut charcoal adsorbs krypton, argon and xenon while helium and neon remain free. The unadsorbed helium and neon are brought in contact with another charcoal maintained at $-{180}^{o}C$ , when neon is adsorbed and helium is obtained in free state. Neon can be recovered from this charcoal on warming.
When the charcoal containing argon, krypton and xenon at $-{100}^{o}C$ is connected with another charcoal maintained at liquid air temperature, the argon diffuses into this charcoal from which it may be obtained by warming. After the separation of argon, the temperature of first charcoal is raised to $-{90}^{o}C$ when pure krypton is evolved. Xenon which remains behind is recovered by further warming the charcoal.

Hence,the correct option is (C).

Note: These elements have their valence shells orbitals completely filled and therefore react with very few elements under ordinary conditions. Hence they are called noble gases.The electronic configuration of noble gases is $n{s}^{2}n{p}^6$ except helium which has configuration $1s^2$ . These are monatomic gases that are colorless, odorless and tasteless.