Unit 1: Solutions - Practice Flashcards

Fundamental vocabulary terms and definitions covering the properties, concentrations, and laws governing solutions as discussed in Unit 1.

Solution

A homogeneous mixture of two or more than two components whose composition and properties are uniform throughout the mixture.

Solvent

The component of a solution present in the largest quantity, which determines the physical state in which the solution exists.

Solute

One or more components present in the solution other than the solvent.

Binary Solution

A solution consisting of exactly two components.

Mass Percentage ($w/w$)

The mass of a component in the solution divided by the total mass of the solution, multiplied by $100$, expressed as: $\frac{\text{Mass of component}}{\text{Total mass of solution}} \times 100$.

Volume Percentage ($V/V$)

Defined as: $\frac{\text{Volume of the component}}{\text{Total volume of solution}} \times 100$.

Mass by Volume Percentage ($w/V$)

Unit commonly used in medicine and pharmacy, defined as the mass of solute dissolved in $100\,mL$ of the solution.

Parts Per Million ($ppm$)

A method to express concentration when a solute is present in trace quantities, defined as: $\frac{\text{Number of parts of the component}}{\text{Total number of parts of all components}} \times 10^6$.

Mole Fraction ($x$)

The ratio of the number of moles of a component to the total number of moles of all components in the solution; the sum of all mole fractions in a solution is unity ($1$).

Molarity ($M$)

The number of moles of solute dissolved in one litre (or one cubic decimetre) of solution, expressed as: $\frac{\text{Moles of solute}}{\text{Volume of solution in litre}}$.

Molality ($m$)

The number of moles of the solute per kilogram ($kg$) of the solvent, expressed as: $\frac{\text{Moles of solute}}{\text{Mass of solvent in kg}}$.

Solubility

The maximum amount of a substance that can be dissolved in a specified amount of solvent at a specified temperature.

Dissolution

The process where a solid solute is added to a solvent and its concentration increases in the solution.

Crystallisation

The process where solute particles in a solution collide with solid solute particles and separate out of the solution.

Saturated Solution

A solution in which no more solute can be dissolved at the same temperature and pressure, and which is in dynamic equilibrium with the undissolved solute.

Unsaturated Solution

A solution in which more solute can be dissolved at the same temperature.

Henry's Law

States that at a constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas ($p$) present above the surface of liquid or solution ($p = K_H x$).

Bends

A painful and dangerous medical condition caused by the formation of nitrogen bubbles in the blood when scuba divers ascend rapidly and pressure decreases.

Anoxia

A condition experienced by climbers at high altitudes where low blood oxygen causes weakness and inability to think clearly due to low atmospheric partial pressure of oxygen.

Vapour Pressure

The pressure exerted by the vapours of a liquid over the liquid phase when they are in equilibrium at a given temperature.

Raoult’s Law

States that for a solution of volatile liquids, the partial vapour pressure of each component of the solution is directly proportional to its mole fraction present in the solution.

Ideal Solutions

Solutions that obey Raoult's law over the entire range of concentration, characterized by $\Delta_{mix}H = 0$ and $\Delta_{mix}V = 0$.

Non-ideal Solutions

Solutions that do not obey Raoult's law, exhibiting either positive or negative deviations in vapour pressure due to differences in molecular interactions.

Azeotropes

Binary mixtures having the same composition in both liquid and vapour phase and which boil at a constant temperature, making separation by fractional distillation impossible.

Colligative Properties

Properties of solutions that depend only on the number of solute particles relative to the total number of particles, and not on the chemical identity of the solute.

Elevation of Boiling Point ($\Delta T_b$)

The increase in the boiling point of a solvent upon adding a non-volatile solute, given by the equation $\Delta T_b = K_b m$.

Ebullioscopic Constant ($K_b$)

Also known as the Molal Elevation Constant; a proportionality constant that depends on the nature of the solvent, measured in $K\,kg\,mol^{-1}$.

Depression of Freezing Point ($\Delta T_f$)

The decrease in the freezing point of a solvent upon the addition of a non-volatile solute, given by $\Delta T_f = K_f m$.

Cryoscopic Constant ($K_f$)

Also known as the Molal Depression Constant; the proportionality constant used to calculate the freezing point depression of a solvent, measured in $K\,kg\,mol^{-1}$.

Osmosis

The process of the flow of solvent molecules from a pure solvent (or a dilute solution) to a solution across a semipermeable membrane.

Semipermeable Membrane (SPM)

A membrane containing a network of submicroscopic pores that allows only small solvent molecules to pass through while hindering larger solute molecules.

Osmotic Pressure ($\Pi$)

The excess pressure that must be applied to a solution to prevent the passage of solvent molecules through a semipermeable membrane into it.

Isotonic Solutions

Two solutions that have the same osmotic pressure at a given temperature and exhibit no osmosis when separated by a semipermeable membrane.

Reverse Osmosis

The phenomenon where the direction of osmosis is reversed by applying a pressure larger than the osmotic pressure to the solution side, commonly used for desalination.

Abnormal Molar Mass

A molar mass value determined experimentally that is either higher or lower than the expected value due to the association or dissociation of solute particles in solution.

van’t Hoff Factor ($i$)

A factor introduced to account for the extent of dissociation or association of a solute; defined as the ratio of the normal molar mass to the abnormal molar mass.