Problem 44 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is not related to colloids? (a) ultrafiltration (b) dialysis (c) Brownian movement (d) wavelength

Step-by-Step Solution

Answer

Wavelength is not related to colloids.

Step 1: Understand Colloids

Colloids are mixtures where very small particles of one substance are evenly dispersed within another. The size of these particles allows them to exhibit unique properties, such as the Tyndall effect and Brownian motion.

Step 2: Examine Each Option

Look at each option: (a) ultrafiltration, (b) dialysis, (c) Brownian movement, and (d) wavelength, to determine their relation to colloids.

Step 3: Analyze Ultrafiltration

Ultrafiltration is a process that uses a membrane to separate particles based on size, often used in removing colloidal particles from solutions. Thus, it is related to colloids.

Step 4: Analyze Dialysis

Dialysis is a process where small molecules are separated from larger molecules by diffusion through a selectively permeable membrane. It can be used to separate colloidal particles, hence is related to colloids.

Step 5: Analyze Brownian Movement

Brownian movement refers to the erratic and random movement of colloidal particles suspended in a liquid or gas. It is a key characteristic of colloids, so it is related to them.

Step 6: Analyze Wavelength

Wavelength pertains to the distance between successive points of a wave, such as light or sound. It is not directly related to the properties or behavior of colloids.

Step 7: Choose the Correct Answer

After analyzing all the options, wavelength does not directly relate to colloids compared to the other options, which are processes or characteristics associated with them.

Key Concepts

Ultrafiltration

Ultrafiltration is a technique used to separate particles based on size using a semi-permeable membrane. This membrane acts like a fine sieve, permitting only small molecules and ions to pass through. Larger molecules and particles, such as those found in colloidal mixtures, are retained.

• It's commonly utilized in the purification of water, where microscopic contaminants need to be removed.
• In the context of colloids, ultrafiltration helps in isolating the colloidal particles from a liquid medium to study their properties in detail.
• Examples of applications include the treatment of waste water and in the dairy industry, for concentrating milk proteins.

This makes ultrafiltration a critical process when dealing with colloids, as it leverages their unique particle size to achieve separation.

Dialysis

Dialysis is a separation process often seen in the biological and chemical industries. It utilizes a selectively permeable membrane to separate small molecules from larger ones or from colloidal particles.

• During dialysis, small ions and molecules diffuse through the membrane, driven by concentration gradients.
• Colloidal particles, being larger, are typically retained by the membrane, a principle used to cleanse blood in kidney dialysis machines.
• In laboratory settings, dialysis can purify proteins, removing unwanted small contaminants from a solution.

This shows that dialysis is closely linked to the study of colloids, especially in the separation and purification of substances.

Brownian Movement

Brownian movement is a noticeable characteristic within colloids. It describes the erratic, zigzag motion of tiny particles suspended in a fluid, either liquid or gas.

• This motion occurs due to collisions with the often smaller, fast-moving molecules of the fluid.
• It's a fundamental property that helps keep colloidal particles from settling, thus stabilizing the colloid.
• The phenomenon was first observed by the botanist Robert Brown and offers evidence of the kinetic theory of particles.

Understanding Brownian movement is crucial to comprehending how colloids behave and remain in suspension.

Wavelength

Wavelength is the distance between successive crests of a wave, typically seen in the context of light and sound.

• While it is a fundamental concept in physics, it does not directly pertain to colloids or their properties.
• Wavelengths are significant in measuring and identifying the different forms of electromagnetic radiation.
• In contrast to the other options related to colloids, wavelength does not define or affect their movement or separation.

Therefore, wavelength stands out as a concept unrelated to the characteristics of colloids, except in certain contexts like studying the Tyndall effect.

Tyndall Effect

The Tyndall effect is a phenomenon observed in colloidal mixtures where light scatters as it hits the particles in suspension. This scattering makes the path of the light beam visible, a feature pronounced in colloids.

• The effect is used to distinguish colloids from true solutions, as true solutions don't scatter light.
• It can be observed when sunlight streams through fog or when dust particles become visible in a ray of sunlight.
• This effect is named after the 19th-century scientist John Tyndall, who studied how light interacts with particulate matter.

The Tyndall effect is integral to understanding colloid systems, demonstrating how their particles interact with light.