Question

What is adsorbed hydrogen by palladium known as?

Answer 1

Adsorption is a very important surface phenomenon of a solid. It comes into existence on account of the residual unbalanced molecular force present at the surface of the solid. In this phenomenon, there is a temporary or permanent deposition of one substance over the surface of some other substance.

Complete answer:
Step 1
The molecular forces are balanced in the interior of a solid or a liquid. These forces are not completely balanced on their surface, therefore are in a state of unsaturation. On account of this, both solid and liquid surfaces have a natural tendency to satisfy their unbalanced force by attaching atoms, molecules, or ions of other substances with which they come in contact.
Step 2
Adsorption of gases on solids is very common. The adsorption of gases on solids is influenced by several factors:
Nature of adsorbent, surface area, and state of subdivision – larger the surface area of the adsorbent, the greater is the amount of the substance it adsorbs.
Nature of the adsorbate – As the gases having high critical temperature can develop van der Waals’ forces more efficiently and can attach readily to the surface hence readily gets adsorbed than the gases having a low critical temperature.
Pressure – Adsorption of gas on solid increases with pressure and achieves a limiting value after achieving a particular concentration.
Temperature – When the gas molecules are attached through van der Waals’ forces, then adsorption decreases with an increase in pressure but if the gas molecules form a chemical bond with the adsorbent, then adsorption first increases and decreases with the rise in temperature.
Step 3
The adsorption of hydrogen on metals like platinum or palladium occurs virtually through a hydride formation and is an example of chemical adsorption or chemisorption. The chemical bonds thus formed cannot be broken easily to release the hydrogen gas from the surface of the metal.

Hence, the adsorbed hydrogen on palladium which is also known as occluded hydrogen which gets absorbed through the hydride formation.

Note:
Occluded hydrogen is used in the hydrogenation of unsaturated organic compounds and converts it into saturated organic compounds. For example, when vanaspati an organic unsaturated compound is treated with occluded hydrogen the saturated ghee is obtained from it.