Problem 55 - A Complete Resource Book in Chemistry for JEE Main

Question

Alum purifies muddy water by (a) absorption (b) dialysis (c) emulsifying properties (d) coagulation

Step-by-Step Solution

Answer

The answer is (d) coagulation.

Step 1: Understanding the Problem

The question asks for the method by which alum purifies muddy water from the given options. We need to identify the correct purification process that alum undergoes.

Step 2: Analyzing the Options

Let's analyze each option to understand the process: - (a) Absorption involves a material taking in another substance. - (b) Dialysis is a process that separates particles in a liquid on the basis of the ability to pass through a membrane. - (c) Emulsifying properties refer to the ability to mix two liquids that usually don't mix. - (d) Coagulation is a process where particles clump together to form larger aggregates.

Step 3: Identifying Alum's Purification Mechanism

Alum purifies muddy water primarily by the process of coagulation. It causes the fine suspended particles in water to clump together into larger particles, making it easier to remove them and thus purify the water.

Step 4: Conclusion

Since coagulation is the process by which alum operates to purify muddy water, the correct answer is (d) coagulation.

Key Concepts

Coagulation

Coagulation is a critical process in water purification that helps in the removal of suspended particles from water. When substances like alum are added to muddy water, they initiate coagulation by neutralizing the electric charge on particles, such as clay or silt.
These particles naturally repel each other due to their similar charges, but when alum is introduced, it causes them to stick together.

How Coagulation Works

• The alum, typically aluminum sulfate, releases aluminum ions when dissolved in water.
• These ions neutralize the charges on the particles.
• With neutralized charges, particles can clump together, forming larger clusters known as "flocs."
• The newly formed flocs are heavier and settle to the bottom or can be filtered easier.

Coagulation thus makes it much simpler to separate out impurities, resulting in clearer water.

Alum Purification

Alum plays a significant role in water purification due to its ability to induce coagulation. Often used in water treatment facilities, alum helps improve water clarity and quality.
One of the key benefits of using alum is its effectiveness in removing turbidity and natural organic matter that cloud the water.

Benefits of Using Alum

• Cost-effective: Alum is widely available and relatively cheap, making it an economical choice for large-scale water treatment.
• Efficiency: It quickly clumps particles, significantly improving the speed of sedimentation.
• Safety: Alum is safe for human consumption in treated water when used in proper amounts.

Alum is not only efficient but also safe. It ensures that purified water meets health and safety standards, providing clean water for communities around the world.

Environmental Chemistry

Environmental chemistry plays a vital role in understanding how various substances affect the natural world, including water purification processes. It explores how chemicals like alum interact with pollutants to enhance water quality.
By understanding the chemical principles behind coagulation, we can optimize water treatment processes, improving resource efficiency and environmental impact.

The Role in Water Treatment

• Environmental chemistry helps identify appropriate coagulating agents, like alum, based on the water's pollutant load.
• It involves analyzing the chemical reactions and environmental consequences of these purification processes.
• Research in environmental chemistry continuously seeks innovative ways to improve the sustainability of water purification methods.

Through a deep understanding of environmental chemistry, we continually improve our ability to provide access to clean and safe water while minimizing environmental impacts.