The solute and solvent in the solution of hydrogen in palladium are

Solute: Gas; Solvent: Solid

The correct answer is Option (1) → Solute: Gas; Solvent: Solid

In a solution of hydrogen in palladium, hydrogen is the component being dissolved (the solute) and palladium is the medium doing the dissolving (the solvent).

This is a unique type of solution known as a solid solution. Specifically, it is a gas-in-solid solution.

• Hydrogen (Solute): Exists as a gas ($H_2$) in its natural state before being absorbed into the metal.
• Palladium (Solvent): Is a transition metal in a solid state. It has a remarkable ability to absorb (occlude) up to 900 times its own volume of hydrogen gas.