Problem 7 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The size of a raw mango shrinks to a much smaller size when kept in a concentrated salt solution. Which one of the following processes can explain this?(a) Osmosis (b) Dialysis (c) Diffusion (d) Reverse osmosis

Step-by-Step Solution

Answer

Osmosis explains the shrinking of the mango in a concentrated salt solution.

Step 1: Understand the Process Involved

To solve this problem, think about what happens to a mango when kept in a concentrated salt solution. The size reduction is due to a movement of water where the water moves out of the mango. We need to determine which process explains this movement.

Step 2: Define Osmosis

Osmosis is the movement of water molecules through a semi-permeable membrane from a region of low solute concentration (inside the mango) to a region of high solute concentration (salt solution). This results in the shrinking of the mango.

Step 3: Consider Other Options

Dialysis is a process that involves the separation of small molecules from large molecules in solution by passing through a membrane. Diffusion is the general movement of particles from high to low concentration and does not specifically involve a membrane. Reverse osmosis involves water moving in the opposite direction, typically using pressure and is mainly used to purify water.

Step 4: Match the Definitions with the Scenario

In this scenario, water moves out of the mango into the salt solution due to the higher solute concentration outside the mango. This matches the definition of osmosis.

Key Concepts

Semi-permeable membrane

In the process of osmosis, a semi-permeable membrane plays a crucial role. This type of membrane allows only certain molecules to pass through it, primarily allowing the free movement of water molecules. Larger solute molecules such as salts or sugars are unable to pass through this barrier, making it selective.
This is important in biological systems, where cells have membranes that act as semi-permeable barriers. They allow cells to regulate their internal environment efficiently.

• Water molecules, being small, can diffuse freely through the membrane.
• Solute molecules are typically larger and cannot pass unless specific pathways are available.
• This selectivity is essential for maintaining the balance of ions and water in cells.

Think of it as a gatekeeper, deciding which substances may enter or exit the cell. In the case of the mango, water molecules exit through this type of membrane, leading to a loss in volume and shrinkage.

Solute concentration

Solute concentration is a key aspect of processes like osmosis. It refers to the amount of solute present in a solution compared to the solvent. In our mango and salt solution example, the salt solution has a high solute concentration while the inside of the mango has a comparatively low solute concentration.
Because osmosis involves the movement of water from areas of low solute concentration to areas of high solute concentration, the solute concentration difference creates a natural drive for water to move.

• Inside the mango: Low solute concentration (more water).
• Outside in the salt solution: High solute concentration (less water).
• This difference leads to water moving out of the mango and into the salt solution.

Thus, the high concentration of solute, such as salt in the solution, prompts water to leave the mango to balance the concentration on both sides of the membrane.

Movement of water molecules

The movement of water molecules is central to the process of osmosis. During osmosis, water molecules move through a semi-permeable membrane from a region where they are in high concentration to a region where they are in lower concentration.
In the context of the mango placed in a concentrated salt solution, the water inside the mango moves out into the salt solution. This movement aims to equalize the solute concentrations on both sides of the membrane.

• Water naturally moves towards areas with higher solute concentration.
• This movement reduces the internal volume of the mango, causing it to shrink.
• This flow continues until equilibrium is reached, where water and solute concentrations are balanced.

Understanding this flow of water molecules helps explain why the mango shrinks as water exits its flesh to move into the salt solution, aligning with the principles of osmosis.