Chemistry Unit 1: Solutions

This set of vocabulary flashcards covers key terms and definitions from the lecture on Solutions, including concentration units, laws of solubility, liquid-liquid behavior, and colligative properties.

Solutions

Homogeneous mixtures of two or more than two components where the 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

The component or components present in a solution in quantities other than the solvent.

Binary solutions

Solutions that consist of only two components.

Mass percentage ($w/w$)

Defined as the ($\text{Mass of the component in the solution}$ / $\text{Total mass of the solution}$) $\times 100$.

Volume percentage ($V/V$)

Defined as the ($\text{Volume of the component}$ / $\text{Total volume of solution}$) $\times 100$.

Mass by volume percentage ($w/V$)

A unit commonly used in medicine and pharmacy, defined as the mass of solute dissolved in $100\text{ mL}$ of the solution.

Parts per million ($\text{ppm}$)

A method to express concentration when a solute is present in trace quantities, defined as the (Number of parts of the component / Total number of parts of all components of the solution) $\times 10^6$.

Mole fraction ($x$)

The ratio of the number of moles of a particular component to the total number of moles of all the components in a solution.

Molarity ($M$)

The number of moles of solute dissolved in one litre (or one cubic decimetre) of solution.

Molality ($m$)

The number of moles of the solute per kilogram ($kg$) of the solvent.

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 in the solution increases.

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.

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 present above the surface of the liquid or solution ($p = K_H x$).

Bends

A painful and life-threatening medical condition for scuba divers caused by nitrogen bubbles blocking capillaries as pressure decreases during ascent.

Anoxia

A condition experienced by people at high altitudes or climbers, where low blood oxygen concentrations lead to weakness and the inability to think clearly.

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 ($p_1 = x_1 p_1^0$).

Ideal solutions

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

Non-ideal solutions

Solutions that do not obey Raoult’s law over the entire range of concentration and exhibit positive or negative deviations from the law.

Azeotropes

Binary mixtures having the same composition in liquid and vapour phase that boil at a constant temperature.

Colligative properties

Properties that depend on the number of solute particles relative to the total number of particles in the solution, irrespective of their chemical nature.

Boiling Point Elevation Constant ($K_b$)

Also known as the Molal Elevation Constant or Ebullioscopic Constant, it relates the elevation of boiling point to the molality of the solution.

Freezing Point Depression Constant ($K_f$)

Also known as the Molal Depression Constant or Cryoscopic Constant, it relates the depression of the freezing point to the molality of the solution.

Semipermeable membranes ($\text{SPM}$)

Membranes, such as pig's bladder or cellophane, that contain submicroscopic pores allowing small solvent molecules to pass while hindering larger solute molecules.

Osmosis

The process involving the flow of solvent molecules through a semipermeable membrane from a pure solvent to a solution.

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 the solution.

Isotonic solutions

Two solutions that have the same osmotic pressure at a given temperature.

Hypertonic

A solution with a higher salt concentration than the fluid inside a cell (e.g., more than $0.9\%\text{ (mass/volume)}$ sodium chloride), causing cells to shrink.

Hypotonic

A solution with a lower salt concentration than the fluid inside a cell, causing water to flow into the cells and make them swell.

Reverse osmosis

The process where pure solvent is squeezed out of a solution through a membrane by applying pressure larger than the osmotic pressure; used in desalination of sea water.

Abnormal molar mass

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

van’t Hoff factor ($i$)

A factor introduced to account for the extent of dissociation or association, defined as the ratio of (Normal molar mass / Abnormal molar mass).