Question

Activated charcoal is used to remove coloring matter from pure substances. It works by:
A. Oxidation
B. Reduction
C. Bleaching
D. Adsorption

Answer 1

Hint: Charcoal is composed of coal, wood, and some other substances. The ordinary charcoal can be converted into “activated charcoal" when high temperature is combined with a gas (activating agent). It helps in expansion of its surface area. Activated charcoal (also called active carbon) is so effective at filtering because it works through the process of adsorption. In other words, a wide range of impurities can chemically adhere to its surface.

Complete step-by-step solution: Ordinary or common charcoal is composed of peat, coal, wood, coconut shell, or petroleum. Manufacturers produce activated charcoal by heating common charcoal in the presence of a gas. As a result of this heating, the charcoal develops a lot of internal spaces known as "pores." Because of the presence of these pores, charcoal becomes active and is able to "trap" chemicals on its surface. This property of trapping chemicals is based on the principle of adsorption. By virtue of this property, activated charcoal is able to remove coloring matter/impurities from substances.

So, the correct option is D.

Note: Uses of activated charcoal-
Because of its toxin-absorbing properties, it is widely used in medicinal chemistry, cosmetic industries.
It also plays an important role in filtering undigested drugs and toxins and thus assists kidney’s function in our body.
It has also got its application in teeth-whitening products.
The capacity of activated charcoal to adsorb is excellent as compared to other adsorbents. But, it is so expensive, having prices ranging from $1000 to $3000 per ton.