Question

Fog is a colloidal solution of:
a.) Liquid particles dispersed in a gas
b.) Gaseous particles dispersed in a liquid
c.) Solid particles dispersed in a liquid
d.) Solid particles dispersed in a gas

Answer 1

Hint: A colloidal solution is a heterogeneous mixture in which the solute particles of around 1-100 nm in size are dispersed in the solvent. The colloidal solution is also heterogeneous in nature like suspension but they have a smaller size of the particles which are distributed.

Complete Solution :
Before answering the question, let us understand what a colloidal solution is.
- We know that a colloidal system is a solution where two substances of different phases are present. Here, very small particles of a substance called the dispersed phase or colloid are distributed through another substance which is the dispersion medium.

Now, let us discuss the colloidal solution given to us in the options.
- Firstly, we have liquid particles dispersed in a gas. Here, the dispersion medium is gas and the dispersed phase is liquid. A system of solids or liquids dispersed in a gas is known as aerosol. Examples of natural aerosols are fog, mist etc.
- Then we have gaseous particles dispersed in a liquid. Here, the dispersion medium is liquid and the dispersed phase is gaseous. Examples include beaten eggs, whipped cream etc.
- Next we have solid particles dispersed in a liquid. Here, the dispersion medium is liquid and the dispersed phase is solid. These are also known as sols. Examples include blood, paint etc.
- Lastly, we have solid particles dispersed in a gas. This is also known as an aerosol but here dispersed particles are solid and the dispersed phase is gas.

Now, in the question we are asked about fog.
- A collection of liquid water droplets or ice crystals suspended in the air at or near the Earth's surface is called fog. We can say that fog is a colloidal solution in which water is the dispersed phase and air is the dispersion medium i.e. liquid dispersed in gas.
So, the correct answer is “Option A”.

Note: Fog is formed when water vapor in the air begins to condense into liquid water. Commonly fog forms at a relative humidity of 100%. Fog formation requires the condensation nuclei.
The dust, aerosol, or pollutants present in the air will act as the condensation nuclei. We cannot see through it because the water droplets hang around the dust and particle nuclei and thus making the vision hazy.