Question

Which of the following is adsorbent?

• A. ZnO
• B. Al\(_2\)O\(_3\)
• C. Fe\(_2\)O\(_3\)
• D. Mn\(_2\)O\(_3\)

Hint:

Common adsorbents in chemistry include activated carbon, silica gel, and activated alumina, all characterized by high surface area and porous structures.

Answer 1

The Correct Option is B

Step 1: Define what an adsorbent is.
An adsorbent is a substance, typically a solid, that possesses a high surface area and a porous structure, allowing it to attract and hold molecules (adsorbates) onto its surface. This process is known as adsorption. Adsorbents are commonly used for purification, separation, and drying processes. Step 2: Analyze the properties of each option.
(A) ZnO (Zinc Oxide): While zinc oxide has various applications, including as a pigment, semiconductor, and catalyst, it is not primarily known or widely utilized as a common adsorbent for general purposes.
(B) Al\(_2\)O\(_3\) (Aluminum Oxide or Alumina): Activated alumina, a highly porous form of aluminum oxide, is a well-known and widely used adsorbent. It has a large surface area and strong affinity for polar molecules, making it effective for drying gases, purifying liquids, and removing fluorides from water. It is also commonly used as a catalyst support.
(C) Fe\(_2\)O\(_3\) (Iron(III) Oxide or Ferric Oxide): Iron(III) oxide is primarily known as a pigment (rust), an ingredient in certain catalysts, and for its magnetic properties. While it can exhibit some adsorption capabilities in specific applications (e.g., arsenic removal), it is not a general-purpose adsorbent in the same class as activated alumina or carbon.
(D) Mn\(_2\)O\(_3\) (Manganese(III) Oxide): Manganese oxides are known for their catalytic activity and ion-exchange properties. They can adsorb certain species, particularly heavy metal ions, but like iron oxide, they are not typically classified as a primary general adsorbent compared to activated alumina. Step 3: Conclude the best adsorbent among the options.
Among the given options, Al\(_2\)O\(_3\) (Alumina), especially in its activated form, is a recognized and widely used adsorbent due to its favorable surface properties and porous structure.