Problem 61 - A Complete Resource Book in Chemistry for JEE Main

Question

The movement of colloidal particles towards the oppositely charged electrodes on passing electric current is known as (a) Tyndall effect (b) cataphoresis (c) Brownian movement (d) none of these

Step-by-Step Solution

Answer

The movement is known as cataphoresis (b).

Step 1: Identify the Keywords

The exercise is about the movement of colloidal particles towards charged electrodes under an electric current. The keyword here is 'movement towards electrodes.'

Step 2: Understand Each Option

Let's consider the options: (a) Tyndall effect - this refers to the scattering of light by particles in a colloid, not related to movement towards electrodes. (b) Cataphoresis - this involves the movement of colloidal particles towards electrodes, also known as electrophoresis. (c) Brownian movement - this refers to the random movement of particles suspended in a fluid. (d) None of these.

Step 3: Choose the Best Option

Since the movement of colloidal particles towards the electrodes matches with 'cataphoresis,' option (b) is the most appropriate.

Key Concepts

Colloidal particles

Colloidal particles are tiny particles that remain suspended in a liquid or gas. They're larger than molecules but too small to settle out or be filtered out easily. This makes them quite stable in suspension. A colloidal system involves two phases: the dispersed phase (particles) and the dispersion medium (fluid or gas). Colloidal particles are vital in various fields like food science, medicine, and materials science.

Some key characteristics of colloidal particles include:

• Size: Typically, they range from 1 to 1000 nanometers.
• Uniform distribution: They are evenly dispersed, preventing them from settling.
• Brownian motion: Random movement that helps maintain their distribution in the medium.

Colloids can exhibit special properties like the Tyndall effect, where they scatter light passing through them. This makes some colloids appear cloudy or opaque under certain lighting conditions.

The movement of colloidal particles becomes particularly interesting in processes like cataphoresis, where electrical charges come into play.

Cataphoresis

Cataphoresis, also referred to as electrophoresis, is the movement of charged colloidal particles under the influence of an electric field. It occurs when an electric current is applied across a dispersion medium containing charged colloidal particles. The charged particles move towards the oppositely charged electrode. This phenomenon is used in various applications, including the separation and analysis of proteins and DNA.

In a typical cataphoresis setup:

• An electric field is applied across a liquid medium with suspended colloidal particles.
• Particles with a negative charge move towards the positive electrode (anode), while positively charged particles move towards the negative electrode (cathode).
• The speed and direction of the particle movement depend on the particle's charge, the electric field's strength, and the medium's characteristics.

Cataphoresis is a critical technique in biotechnology and medicine. It allows for the precise manipulation and study of molecules within a colloidal suspension.

Electric current

Electric current is the flow of electric charge through a conductor. It's essential for powering various devices and systems, including those used in electrophoresis and cataphoresis processes. In simple terms, an electric current flows when there is a difference in electric potential, often referred to as voltage, across a conductor.

There are two main types of electric current:

• Direct Current (DC): Electric charge flows in one direction. It's commonly used in batteries.
• Alternating Current (AC): Electric charge periodically changes direction. It's commonly used in household power supplies.

In cataphoresis, the electric current creates an electric field that causes charged colloidal particles to move towards electrodes. The strength and direction of the electric current greatly influence the rate and efficiency of the particle movement. Understanding electric current is critical in designing and optimizing systems for scientific research and industrial applications.