Problem 137 - A Complete Resource Book in Chemistry for JEE Main

Question

Freshly prepared precipitate sometimes gets converted to colloidal solution by (a) Electrolysis (b) Coagulation (c) Peptisation (d) Diffusion

Step-by-Step Solution

Answer

Peptisation

Step 1: Understanding Precipitate Conversion

In this exercise, we need to identify the process by which a freshly prepared precipitate can be converted into a colloidal solution. This transformation involves breaking down the larger particles of the precipitate into smaller, colloidal size particles.

Step 2: Exploring Options

Let's examine the given options: - **Electrolysis** typically involves the use of electrical currents to drive a chemical reaction but does not directly relate to forming colloids from precipitates. - **Coagulation** is the process of aggregating colloidal particles to form a precipitate, which is the reverse of what we want. - **Peptisation** specifically refers to the dispersion of a precipitate into colloidal particles by adding an agent (peptizing agent). - **Diffusion** is the movement of particles from high to low concentration and does not apply to colloid formation from precipitates.

Step 3: Applying Knowledge

From examining the options, we identify that the process of **peptisation** involves the addition of a suitable peptizing agent to a freshly precipitated substance, which prevents the particles from coming together and thus forms a stable colloidal solution.

Step 4: Conclusion

The correct answer is that freshly prepared precipitate is converted to a colloidal solution by the process of **peptisation**.

Key Concepts

Precipitate Conversion

When a freshly prepared precipitate is changed into a colloidal solution, we are talking about precipitate conversion. This is a fascinating process in the realm of Chemistry, where large particles that have settled out from a solution undergo transformation into much smaller, suspended particles, thus forming a colloid.
The key aspect of precipitate conversion is breaking down particles to colloidal size, which ranges from 1 to 1000 nanometers. These tiny particles remain dispersed throughout the medium, appearing as a homogeneous mixture. This conversion is vital to various industrial and scientific applications, as colloids have unique properties such as higher surface area and stability.

Peptisation

Peptisation is a critical process in forming colloidal solutions from precipitates. It involves adding a substance known as a peptizing agent, which stabilizes the particles of the precipitate. When a peptizing agent is introduced, it absorbs onto the surface of the particles, often imparting an electric charge. This charge prevents particles from coalescing.
Common examples of peptizing agents include electrolytes like certain acids or bases. These agents ensure that the precipitate does not clump together, and instead forms a stable, evenly dispersed colloid.
Peptisation can be illustrated by adding hydrochloric acid to freshly precipitated ferric hydroxide, effectively changing it into a colloidal form. The electric charge imparted by the chloride ions from the acid keeps the particles from settling.

Chemistry Education

The study of Chemistry offers insights into numerous practical applications, processes, and phenomena around us. Chemistry education not only fosters an understanding of substances and their interactions but also develops critical thinking.
In the context of colloidal systems, students learn about the behaviours and characteristics of these mixtures which differ from simple solutions and suspensions. Experimenting with colloids can be a hands-on experience that promotes inquiry, observation, and analysis skills.
Concepts like peptisation and precipitate conversion are critical components of the Chemistry curriculum. They form a foundation for more advanced studies in material sciences and industrial chemistry.

Colloids

Colloids are systems where fine particles are suspended throughout a continuous medium. These particles are larger than a molecule but too small to settle out under gravity. Colloids exhibit unique optical, physical, and chemical properties.
A colloid's optical property is often demonstrated through the Tyndall effect, where light scatters as it passes through the colloidal particles. This is why fog (a colloid) looks opaque in headlights.
Types of colloids vary based on the state of the dispersed phase and the dispersion medium, including sols, gels, emulsions, and aerosols.

• Sol: solid particles in a liquid
• Gel: a liquid in a solid
• Emulsion: liquid in a liquid
• Aerosol: liquid or solid in a gas

Understanding colloids is essential as they are present in countless everyday products, from milk to paint.

JEE Main Chemistry

JEE Main Chemistry is a crucial segment of this prestigious engineering entrance examination in India. It encompasses diverse topics such as physical chemistry, organic chemistry, and inorganic chemistry.
The study of colloidal chemistry is part of the curriculum and involves mastering concepts like precipitates, colloids, and processes such as peptisation. Such topics are not only interesting but also test the student's comprehensive understanding of chemistry fundamentals.
Excelling in JEE Main Chemistry requires a deep understanding of theoretical concepts backed by problem-solving skills. Students are encouraged to engage in practical experiments and applications, fostering a thorough grasp of subjects like colloid chemistry which often feature in examinations.