chapter 14 Colligative Properties, Solution Equilibrium, and Solution Energetics

Vocabulary flashcards covering colligative properties, solution equilibria, Henry's law, solubility factors, and solution formation energetics from Chemistry lecture notes.

Colligative property

A property of a solution that depends on the number of particles dissolved in the solution, not the type of particle.

Vapor pressure lowering

A colligative property where the vapor pressure of a solution is lower than the vapor pressure of the pure solvent.

Vapor pressure lowering equation

The mathematical relationship expressed as $P_{\text{solution}} = X_{\text{solvent}} P^\text{o}_{\text{solvent}}$.

Freezing point depression

A colligative property where the freezing point of a solution is lower than the freezing point of the pure solvent.

Boiling point elevation

A colligative property where the boiling point of a solution is higher than the boiling point of the pure solvent.

Strong electrolyte solutions in colligative properties

Solutions that produce more colligative properties than non-electrolyte solutions because they dissociate into a greater number of particles.

Solubility

The amount of a substance that dissolves in a given amount of solvent.

Saturated solution

A solution in which the dissolved solute is in dynamic equilibrium with the solid (undissolved) solute; the amount of dissolved solute equals the solubility, so added solute will not dissolve.

Unsaturated solution

A solution containing less than the equilibrium amount of solute; if additional solute is added, it will dissolve.

Supersaturated solution

An unstable solution containing more than the equilibrium amount of solute, which will normally precipitate out of the solution.

Solubility of NaCl in water

Equals $35\text{ g}/100\text{ g}$ water at $25\text{ }^\text{o}\text{C}$; if added beyond $35\text{ g}$, the excess will stay solid and will not dissolve.

Henry's law

A law quantifying gas solubility with increasing pressure using the equation $S_{\text{gas}} = k_H P_{\text{gas}}$, showing solubility is directly proportional to partial pressure.

$$S_{\text{gas}}$$

The solubility of a gas in Henry's law, usually expressed in units of molarity ($M$).

$$k_H$$

The constant of proportionality in Henry's law, called the Henry's law constant.

$$P_{\text{gas}}$$

The partial pressure of a gas above a liquid in Henry's law, usually expressed in atmospheres ($\text{atm}$).

Temperature effect on solid and liquid solubility

The general trend where solubility of solids and liquids increases with an increase in temperature.

Temperature effect on gas solubility

The trend where solubility of gases in liquids decreases with increasing temperature.

Exothermic solution process ($|\text{a}H_{\text{solute}}| < |\text{a}H_{\text{hydration}}|$)

A process where releasing energy when water wraps around ions gives off more heat than it takes to pull solute apart, releasing extra heat ($\text{a}H < 0$) and making the solution feel warm.

Endothermic solution process ($|\text{a}H_{\text{solute}}| > |\text{a}H_{\text{hydration}}|$)

A process where pulling solute apart takes more energy than water gives back, stealing heat from surroundings ($\text{a}H > 0$) and making the solution feel cold.

Enthalpy of solution ($\text{a}H_{\text{soln}}$)

According to Hess's law, the overall enthalpy change upon solution formation given by $\text{a}H_{\text{soln}} = \text{a}H_{\text{solute}} + \text{a}H_{\text{solvent}} + \text{a}H_{\text{mix}}$.

$$\text{a}H_{\text{solute}}$$

The positive (endothermic) energy required to break apart the solute particles.

$$\text{a}H_{\text{mix}}$$

The exothermic step ($\text{a}H_{\text{mix}} < 0$) where energy is released as solute particles interact with solvent particles through intermolecular forces.

Heat of hydration ($\text{a}H_{\text{hydration}}$)

The combination of $\text{a}H_{\text{solvent}}$ and $\text{a}H_{\text{mix}}$ into a single term for aqueous solutions, which is always largest and negative (exothermic) for ionic compounds.