Question

After removing the hard shell of an egg by dissolving in dilute \(\mathrm{HCl}\), a semipermeable membrane can be visible. If such an egg is kept in a saturated solution of common salt, the size of egg will (a) shrink (b) grow (c) remain unchanged (d) first shrink, then grow

Short answer

The size of the egg will shrink due to osmosis.

Step-by-step solution

Understand Osmosis

Osmosis is the movement of water molecules from a region of lower solute concentration to a region of higher solute concentration through a semipermeable membrane.

Analyze Solvent and Solute Concentrations

The interior of the egg likely has a lower solute concentration compared to the saturated salt solution. Hence, water molecules will move from the inside of the egg to the outside, trying to balance the solute concentrations.

Predict the Changes in Size

Due to the outward movement of water from the egg, the egg will lose water and therefore, the size of the egg will shrink.

Key concepts

Semipermeable Membrane

The role of a semiperpermeable membrane is central to the process of osmosis. It functions as a selective barrier that allows certain types of molecules or ions to pass through, while blocking others. Think of it as a bouncer at a club, only letting VIP guests (in this case, usually water molecules) through and keeping the rest (larger molecules or solutes) out.

For instance, in our egg experiment, the membrane around the egg acts like this bouncer. After the shell has been removed, the egg's membrane is exposed, ensuring that only water, and not salt or other large solutes, can move in and out freely. This selective permeability is crucial; without it, osmosis as we understand it wouldn’t occur, as all substances would pass through without regulation.

Solute Concentration

Solute concentration refers to the amount of solute - which are the dissolved substances, such as salt, sugar, or minerals - within a solvent, like water. In terms of osmosis, the concentration gradient is the driving force that determines the direction water will move.

Osmosis seeks to balance concentrations on either side of the semipermeable membrane such that the concentration of solute is equal. Higher solute concentration means less free water and vice versa. In the context of our experiment, the saturated salt solution outside the egg contains a high concentration of salt, considerably more than what is inside the egg. This concentration difference is the critical element that predicts the flow of water.

Movement of Water Molecules

Water molecules are like social creatures; they tend to move towards areas where they're less concentrated to create balance. This balance-seeking process is known as osmosis.

During osmosis, water molecules naturally flow from an area of low solute concentration (where there are more free water molecules) to one of high solute concentration (where free water molecules are fewer) through the semipermeable membrane. This movement is driven by the water concentration gradient and will continue until equilibrium is reached, meaning solute concentrations are even on both sides of the membrane.

In our egg exercise, this translates to water moving out of the egg and into the salty exterior, leading to shrinkage—a visual and tangible effect of osmosis in action.