Problem 34 - Chemistry in 30 days

Question

fcaction. Alum helps in purifying water by (a) forming Si complex with clay particies. (b) sulphate part which combines with dirt and removes it. (c) aluminum which coagulates the mud particle. (d) making mud water-soluble.

Step-by-Step Solution

Answer

(c) aluminum which coagulates the mud particle.

Step 1: Identify the Function of Alum

Alum is a compound used in the process of purifying water. To understand its function, we need to consider which components of alum are involved in the purification process.

Step 2: Understand Coagulation

Alum is primarily used for its coagulating properties. Coagulation refers to the process where small particles in suspension are aggregated into larger particles, which can then be removed more easily from the water.

Step 3: Determine the Active Component

The active component of alum in coagulation is aluminum. It's the aluminum ions that help to coagulate or clump the mud and dirt particles present in water.

Step 4: Choose the Correct Option

Given the options, we need to choose the one that describes the role of aluminum in coagulating mud particles. The correct statement is related to aluminum aggregating particles.

Key Concepts

Alum Coagulation

When we talk about water purification, alum coagulation is a critical process. Coagulation refers to the transformation of small particles suspended in the water into larger clumps. These larger particles are easier to remove, allowing for cleaner water. Alum, a chemical compound, facilitates this process effectively. It achieves this by neutralizing the charge on particles. By adding alum to water, suspended particles that carry a charge repel each other under normal circumstances begin to clump together.
• This absence of repulsion allows for the formation of larger particles known as "flocs."
• These flocs can then be easily filtered out or settled out of the water, making the purification process much more effective.

Aluminum Ions

The role of aluminum ions in the process of coagulation is pivotal. Alum's ingredient responsible for this is aluminum sulfate, which breaks down to release aluminum ions in water. These aluminum ions carry a positive charge. The positive charge is essential, as it interacts with negatively charged particles like clay, silt, or organic material suspended in water.
• Upon interaction, the aluminum ions neutralize the charges on these particles.
• Neutralization means these once-repelling particles now come together to form larger aggregates. Such flocs can then be removed easily, improving the water's clarity and quality.

Mud Particle Removal

Removing mud particles from water is integral in making it safe for consumption. The process heavily relies on the formation of flocs during alum coagulation. Once coagulation takes place, the removal process involves either filtration or sedimentation.
• In filtration, the water passes through filters that capture heavy flocs, leaving behind cleaner water.
• In sedimentation, gravity helps larger flocs settle at the bottom, which can then be physically removed. This step ensures the removal of impurities and mud, pivotal in providing safe water.
The presence of aluminum ions considerably enhances this removal process by forming larger and heavier flocs, ensuring efficiency in purification.