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

Question

The turbidity of a polymer solution measures (a) light transmitted by the solution (b) light scattered by the solution (c) a light absorbed by solution (d) none of these

Step-by-Step Solution

Answer

(b) light scattered by the solution.

Step 1: Identify Key Concepts

Understand what turbidity refers to in terms of a solution. Turbidity is generally associated with the clarity of a fluid due to the presence of suspended particles.

Step 2: Define Turbidity Properly

Turbidity is the measure of the degree to which light is scattered by particles in a liquid. The more particles present, the more light is scattered.

Step 3: Analyze Options

Evaluate each choice based on the definition of turbidity: - Option (a) 'light transmitted by the solution': refers to the amount of light passing through with minimal scattering. - Option (b) 'light scattered by the solution': matches the definition of turbidity as it indicates how much light is deflected by particles in the solution. - Option (c) 'a light absorbed by solution': this is related to absorbance, not turbidity. - Option (d) 'none of these': already ruled out by the match seen in option (b).

Step 4: Choose the Correct Option

Based on the definition of turbidity as the scattering of light by particles, the correct answer here is option (b) 'light scattered by the solution.'

Key Concepts

Light scattering in solutions

In a solution, light scattering occurs due to the interaction of light with suspended particles. When light hits these particles, it is deflected in various directions. This phenomenon is most noticeable when there are visible particles present, but it also occurs at microscopic levels. Light scattering is a critical principle in understanding turbidity, as it directly impacts the clarity of a solution.

The degree of scattering depends on several factors:

• The size and concentration of the particles: Larger and more numerous particles cause more scattering.
• The wavelength of the light: Different wavelengths scatter to different extents.
• The angle of observation: Scattered light is observed at angles to the incident light, where intensity varies with angle.

Understanding these variables is essential in predicting and measuring solution turbidity effectively.

Polymer solution properties

Polymer solutions are unique because the polymers can significantly alter the physical behavior of the solution. When polymers dissolve, their chains can become entangled, affecting properties such as viscosity, elasticity, and the ability to scatter light.
Polymers, given their substantial size and complex structures, increase turbidity compared to solutions with smaller, simpler molecules:

• Size of polymer molecules: Larger polymers scatter more light, increasing turbidity.
• Concentration of polymer: Higher concentrations lead to more entanglement, affecting clarity and light scattering.
• Interactions between polymer and solvent: Certain solvent-polymer combinations lead to more scattering due to differences in refractive indices.

These factors are crucial in industries utilizing polymer solutions for specific clarity and structural requirements.

Solution clarity measurement

Measuring the clarity of a solution involves assessing how clear or turbid it is. Turbidity is a common measure used to determine this, as it directly relates to the scattering of light by suspended particles. The clearer a solution, the less scattered the light.
Common methods for measuring turbidity include:

• Turbidimeters: Devices that quantify the amount of scattered light at specific angles from the incident beam.
• Nephelometers: Instruments specialized in measuring scattered light in a particular direction, providing a detailed turbidity profile.

Understanding solution clarity is essential in fields like water treatment, beverage production, and any processes where visual appearance impacts product quality. By accurately measuring turbidity, industries can ensure product consistency and compliance with clarity standards.