Substance employed as drying agents are usually?

Analysis of the Question

The question asks for the property of substances that are used as "drying agents." In chemistry, a drying agent (or desiccant) is a substance that removes moisture from its surroundings, such as from gases or other chemical compounds.

Explanation of Concepts

To identify the correct answer, let's look at the definitions of the terms provided in the options:

• Amphoteric: These are substances that can react as both an acid and a base (e.g., Aluminum oxide). This property does not determine whether a substance can absorb water.
• Hygroscopic: These are substances that have the ability to absorb moisture from the atmosphere. Because they "soak up" water vapor, they are ideal for use as drying agents in the laboratory.
• Efflorescent: These are hydrated salts that lose their water of crystallization to the atmosphere when exposed to air. They do the opposite of drying agents; they release water.
• Acidic: This refers to the pH level of a substance. While some drying agents (like concentrated tetraoxosulphate(VI) acid) are acidic, being acidic is not the defining characteristic that makes a substance a drying agent.

Step-by-Step Solution

1. Define the role: A drying agent must be capable of attracting and holding water molecules from the environment.
2. Evaluate the options: • An efflorescent substance loses water, so it cannot be a drying agent. • Amphoteric and acidic are chemical properties related to reactivity and pH, not necessarily water absorption. • A hygroscopic substance actively absorbs water from the air or from a substance it is in contact with. This is the exact definition of a drying agent.
3. Conclusion: Since hygroscopic substances naturally attract and retain water, they are the standard materials used to dry gases or keep environments moisture-free.

Identify the Answer

The correct option is B.

Exam Tip

To remember this easily, think of the word "Hygro" (related to humidity/water) and "Scopic" (like a scope, reaching out to grab). A hygroscopic substance "reaches out" to grab water from the air. Conversely, remember that efflorescent starts with "E" for "Exit"—the water is exiting the substance!