Which of the following materials acts as the best adsorbent due to its very high surface area and is commonly used to remove impurities, colours and odours from gases and liquids?

Introduction / Context:
Adsorption is a surface phenomenon in which molecules from a gas or liquid accumulate on the surface of a solid. Some materials have extremely high surface area and are very effective adsorbents, used for purification, decolourisation and deodorisation. This question asks which material acts as the best adsorbent among the options. Understanding the role of activated materials helps students connect colloid and surface chemistry with practical purification methods.

Given Data / Assumptions:

• We are comparing various carbon based materials and one non carbon material for their adsorbing ability.
• Adsorption efficiency depends strongly on surface area and pore structure.
• The best adsorbent among the choices should have a very high internal surface area.
• Context is general laboratory and industrial purification.

Concept / Approach:
Activated charcoal is produced by heating carbon rich materials such as coconut shells or wood in the absence of air and then activating them to create a network of fine pores. This activation greatly increases the internal surface area, often to hundreds or even thousands of square metres per gram. As a result, activated charcoal can adsorb large amounts of gases, dyes and other impurities. Ordinary charcoal, carbon black and coconut shell charcoal have lower accessible surface area unless specifically activated. Silica gel is also a good adsorbent for moisture, but in many school level treatments, activated charcoal is highlighted as the best general purpose adsorbent.

Step-by-Step Solution:

Verification / Alternative check:
Lab manuals often recommend activated charcoal for decolourising sugar solutions and for removing organic impurities from solutions because of its powerful adsorbing action. Gas masks and water filters frequently use activated carbon granules to trap toxic vapours and odours. Technical data sheets for activated charcoal report extremely high specific surface areas, much greater than those of untreated charcoal or simple carbon black. Although silica gel also has a high surface area and is used in desiccant packets, exam questions on adsorption typically emphasise activated charcoal as the most effective adsorbent overall.

Why Other Options Are Wrong:

• Charcoal: Has some adsorbing capacity but is less effective than properly activated charcoal due to lower porosity and surface area.
• Coconut shell charcoal: A good raw material for making activated charcoal, but before activation its adsorption capacity is lower.
• Carbon black: Consists of small carbon particles used mainly as pigment and reinforcing filler; not highlighted as the strongest adsorbent in school chemistry.
• Silica gel: An important adsorbent for moisture control, but in the context of general adsorption questions, activated charcoal is commonly regarded as superior for a broad range of substances.

Common Pitfalls:
Students may see several carbon based options and feel unsure which is best. Some may choose silica gel because it is familiar from desiccant packets in packaging. To avoid confusion, remember that activated charcoal is specially processed to maximise adsorption and is widely used in gas masks, water purifiers and decolourisation. Ordinary charcoal and coconut shell charcoal become much better adsorbents only after activation. Associating the word activated with improved performance can help in recalling the correct answer.

Final Answer:
The material that acts as the best adsorbent among the options is Activated charcoal.