key term - Semipermeable Membrane

Definition

A semipermeable membrane is a thin, selective barrier that allows certain molecules or ions to pass through while restricting the passage of others. This type of membrane is crucial in various biological and chemical processes, including the colligative properties discussed in the 11.4 chapter.

5 Must Know Facts For Your Next Test

1. Semipermeable membranes allow the passage of small, uncharged molecules, such as water, while restricting the movement of larger molecules and ions.
2. The selective permeability of semipermeable membranes is crucial in maintaining concentration gradients and osmotic balance in biological systems.
3. Colligative properties, such as boiling point elevation and freezing point depression, are influenced by the presence of a semipermeable membrane and the movement of solvent molecules across it.
4. Semipermeable membranes are used in various industrial and technological applications, including water purification, dialysis, and fuel cells.
5. The structure and composition of semipermeable membranes can be engineered to control the selective transport of specific molecules or ions, making them valuable in a wide range of applications.

Review Questions

• Explain how the selective permeability of a semipermeable membrane affects the colligative property of boiling point elevation.
  • The selective permeability of a semipermeable membrane allows water molecules to pass through, while restricting the passage of dissolved solute particles. This creates a concentration gradient, where the solute concentration is higher on one side of the membrane compared to the other. According to Raoult's law, the presence of dissolved solutes in a solution decreases the vapor pressure of the solvent, which in turn increases the solution's boiling point. The semipermeable membrane maintains this concentration gradient, allowing the colligative property of boiling point elevation to occur.
• Describe the role of a semipermeable membrane in the process of osmosis and how it relates to the colligative property of freezing point depression.
  • In the context of colligative properties, a semipermeable membrane plays a crucial role in the process of osmosis. Osmosis is the spontaneous movement of water molecules from a region of lower solute concentration (higher water concentration) to a region of higher solute concentration (lower water concentration) through the semipermeable membrane. This movement of water molecules is driven by the concentration gradient and serves to equalize the solute concentrations on both sides of the membrane. The presence of the semipermeable membrane and the resulting osmotic pressure difference contribute to the colligative property of freezing point depression, where the addition of solutes to a solvent (e.g., water) lowers the freezing point of the solution.
• Evaluate the importance of semipermeable membranes in various applications, such as water purification, dialysis, and fuel cells, and how their selective permeability is leveraged in these contexts.
  • Semipermeable membranes are essential in a wide range of applications due to their ability to selectively allow the passage of certain molecules or ions while restricting others. In water purification, semipermeable membranes are used in processes like reverse osmosis to remove impurities and contaminants, producing clean, purified water. In dialysis, semipermeable membranes are used to filter waste and excess water from the blood, mimicking the function of healthy kidneys. In fuel cells, semipermeable membranes, such as proton exchange membranes, facilitate the selective transport of protons while preventing the mixing of reactants, improving the efficiency and performance of the fuel cell. The engineering of semipermeable membranes with tailored permeability characteristics is crucial in optimizing these and other applications that rely on the selective transport of molecules or ions.

Related terms

Osmosis:

The spontaneous movement of water molecules through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration, equalizing the solute concentrations on both sides of the membrane.

Dialysis:

A process that uses a semipermeable membrane to selectively remove waste, surplus water, and other impurities from the blood, as in the case of kidney dialysis.

Diffusion:

The net movement of molecules or ions from a region of higher concentration to a region of lower concentration through a semipermeable membrane, driven by the concentration gradient.