Question

An example of solid solution is:
(A) butter
(B) gemstones
(C) paint
(D) hair cream

Answer 1

Hint: Solids are colloidal solutions in which both the dispersed phase and the dispersion medium are solids. To solve this question we need to classify each of the options based on the dispersed phase and the dispersion medium present in them.

Complete step by step solution:
In order to solve this question we first need to understand about colloids.
Colloids are mixtures in which the particles of one substance are dispersed throughout a second substance. The substance whose particles are dispersed is called the dispersed phase and the substance in which the particles of another substance are dispersed is called the dispersion medium. The size of the colloidal particles is generally between 1 micro-meter and 1 Nano-meter. Both the dispersed phase and the dispersion medium could be solid, liquid or a gas. The formation of colloids could be reversible or irreversible. Colloidal solutions display Tyndall effect (when beams of light are incident on a colloidal solution, they get scattered).
Stable colloids are also called lyophilic sols since strong forces of attraction are present between the dispersed phase and the dispersion medium. They can be prepared by using a variety of methods such as chemical methods (oxidation, double decomposition, reduction, hydrolysis etc.) and dispersion methods (mechanical dispersion, Bredig’s arc method, peptization etc.).
We can classify colloids based on a number of parameters such as physical state, the dispersion medium, interactive forces present and properties of sol particles.
Classification in terms of the physical state:
(i) Solid solution/solid sol: Both the dispersed phase and the dispersion medium are solid.
(ii) Aerosol: Air is the dispersion medium while the dispersed phase could be liquid, solid or gas. Example: clouds (air is the dispersion medium and water droplets are the dispersed phase), smoke (air is the dispersion medium while carbon particles are the dispersed phase) etc.
(iii) Gels: The dispersion medium is solid while the dispersed phase is liquid. For example butter.
(iv) Emulsion: Both the dispersed phase and the dispersion medium are liquids. For example, milk, vanishing cream etc.
Butter is a gel, hair cream is an emulsion while in paint the dispersed phase is solid and the dispersion medium is liquid. Gemstones are solid sols.

Hence the correct answer is (B) gemstones.

Note: Many gemstones contain transition metal ions which are also responsible for their colour due to d-d transitions. For example Ruby is an alumina ${ Al }_{ 2 }{ O }_{ 3 }$ containing around 0.5-1% ${ Cr }^{ 3+ }$ ions that are randomly present at the site of ${ Al }^{ 3+ }$ ions in the lattice.