Physical Chemistry Lecture - 14: Solutions

Flashcards covering the properties of solutions, specifically osmosis, osmotic pressure, and depression in freezing point based on the lecture material.

Molal depression constant ($K_f$)

A property of the solvent that remains unchanged even if the molality of the dilute solution is modified.

Freezing Point

The temperature at which the vapour pressure of the substance in its liquid phase equals its vapour pressure in the solid phase.

Osmosis

The movement of solvent molecules through a semi-permeable membrane from a pure solvent to a solution or from a less concentrated solution to a more concentrated solution.

Semi-permeable membrane (SPM)

A membrane that allows only solvent particles to pass through while remaining impermeable to solute particles.

Natural semi-permeable membrane

Examples of biological membranes that act as semi-permeable barriers, such as an animal bladder or a plant bladder.

Artificial semi-permeable membrane

Synthetically prepared membranes used in osmosis, such as cellulose acetate or $Cu_2[Fe(CN)_6]$.

Osmotic Pressure ($\pi$) (Hydrostatic Definition)

The hydrostatic pressure built up on the solution side or more concentrated side due to the movement of solvent particles through a semi-permeable membrane, calculated as $\pi = \rho g h$.

Osmotic Pressure ($\pi$) (Chemical Definition)

The pressure associated with a solution's concentration, described by the formula $\pi = CRT$, where $C$ is the molarity, $R$ is the universal gas constant, and $T$ is the temperature.

Universal gas constant ($R$)

A constant used in the osmotic pressure equation, with values such as $0.0821\,L\,atm\,mol^{-1}\,K^{-1}$, $8.314\,J\,mol^{-1}\,K^{-1}$, or approximately $\frac{1}{12}\,L\,atm\,mol^{-1}\,K^{-1}$.

Vapour Pressure Condition for Freezing

Freezing occurs when the vapour pressure of the solid solvent is equal to the vapour pressure of the pure solvent or the solution.