Chemistry Lecture Notes: Solutions

Vocabulary flashcards covering key terms, concentration units, laws, graphs, and colligative properties from the chapter on Solutions.

Solution

A homogeneous mixture of two or more substances in same or different physical phases.

Binary Solution

A solution consisting of two components, a solute and a solvent.

Solute and Solvent

In a binary solution, the solvent is the component present in a large quantity, while the solute is the component present in a small quantity.

Aqueous and Non-Aqueous Solutions

An aqueous solution is one where water is used as the solvent, whereas a non-aqueous solution uses a solvent other than water.

Unsaturated Solution

A solution in which more solute can be dissolved without raising temperature.

Saturated Solution

A solution in which no more solute can be dissolved further at a given temperature.

Supersaturated Solution

A solution which contains more solute than that would be necessary to saturate it at a given temperature.

Percentage by Weight ($\text{w/w }\%$)

The amount of solute present in $100\,\text{g}$ of solution, defined as $\text{w/w }\% = \frac{\text{weight of solute}}{\text{weight of solution}} \times 100$.

Percentage by Volume ($\text{v/V }\%$)

The volume of solute present in $100\,\text{mL}$ of solution, defined as $\text{v/V }\% = \frac{\text{volume of solute}}{\text{volume of solution}} \times 100$.

Mole Fraction ($\chi$)

The ratio of the number of moles of a component to the total number of moles of all the components in solution, where $\chi_A + \chi_B = 1$.

Parts Per Million ($\text{ppm}$)

The parts of a component per million parts ($10^6$) of the solution, expressed as $\text{ppm} = \frac{\text{number of parts of the component}}{\text{total number of parts of all components}} \times 10^6$.

Molarity ($M$)

The number of moles of solute present in $1\,\text{L}$ ($1\,\text{dm}^3$) of the solution, expressed in units of $\text{g-mol/L}$; it varies with temperature due to volume changes.

Molality ($m$)

The number of moles of solute per kilogram ($1\,\text{kg}$) of the solvent, expressed in units of $\text{g-mol/kg}$; it is independent of temperature.

Normality ($N$)

The number of gram equivalents of solute present in $1\,\text{L}$ of solution, related to molarity by $N \times \text{equivalent weight} = M \times \text{molecular weight}$.

Formality ($F$)

The number of formula weights of solute present per litre of the solution, given by $\text{Formality} = \frac{\text{moles of substance added to solution}}{\text{volume of solution in L}}$.

Demal ($D$)

A concentration unit representing one mole of solute present in $1\,\text{L}$ of solution at $0^\circ\text{C}$.

Solubility

The maximum amount of a solute that can be dissolved in a given amount of solvent (generally $100\,\text{g}$) at a given temperature.

Henry's Law

States that the partial pressure ($p$) of a gas in vapour phase is proportional to the mole fraction ($x$) of the gas in solution: $p = K_H x$.

Anoxia

A medical condition caused by low concentrations of $\text{O}_2$ in the blood of climbers at high altitudes due to lower partial pressure of oxygen.

Vapour Pressure

The pressure exerted by the vapour molecules above the liquid surface in equilibrium with the liquid at a given temperature.

Raoult's Law

States that for a solution of two volatile liquids, the partial vapour pressure of each liquid is directly proportional to its mole fraction: $p_A = p_A^\circ \chi_A$.

Ideal Solution

A solution where solute-solute ($\text{B--B}$) and solvent-solvent ($\text{A--A}$) interactions are almost similar to solvent-solute ($\text{A--B}$) interactions, satisfying Raoult's law with $\Delta H = 0$ and $\Delta V = 0$.

Non-Ideal Solution Showing Positive Deviation

A solution where $\text{A--B}$ interactions are weaker than $\text{A--A}$ or $\text{B--B}$ interactions, resulting in higher vapour pressure than predicted by Raoult's law, with $\Delta H > 0$ and $\Delta V > 0$.

Non-Ideal Solution Showing Negative Deviation

A solution where $\text{A--B}$ interactions are stronger than $\text{A--A}$ or $\text{B--B}$ interactions, resulting in lower vapour pressure than predicted by Raoult's law, with $\Delta H < 0$ and $\Delta V < 0$.

Azeotropic Mixture

A mixture of two liquids which boils at a constant temperature like a pure liquid and distils over in the same composition.

Colligative Properties

Properties of a solution that depend only upon the number of solute particles present in the solution, irrespective of their nature.

Relative Lowering of Vapour Pressure

The ratio of lowering in vapour pressure to the vapour pressure of pure solvent, equal to the mole fraction of the non-volatile solute: $\frac{p^\circ - p}{p^\circ} = \chi_B$.

Elevation in Boiling Point ($\Delta T_b$)

The increase in boiling point of a solvent when a non-volatile solute is added, calculated as $\Delta T_b = K_b m$.

Molal Elevation Constant ($K_b$)

Also known as ebullioscopic constant, it represents the boiling point elevation for a $1\,\text{m}$ solution; for water, $K_b = 0.52\,\text{K\,kg\,mol}^{-1}$.

Depression in Freezing Point ($\Delta T_f$)

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

Osmosis

The spontaneous flow of solvent molecules through a semipermeable membrane from pure solvent to solution or from a dilute solution to a concentrated solution.

Osmotic Pressure ($\pi$)

The hydrostatic pressure developed on a solution that prevents the osmosis of pure solvent into it through a semipermeable membrane, calculated as $\pi = CRT$.

Hypertonic Solution

A solution having a higher osmotic pressure than another solution from which it is separated by a semipermeable membrane, causing cell shrinkage (plasmolysis).

Hypotonic Solution

A solution having a lower osmotic pressure than another solution from which it is separated by a semipermeable membrane.

Isotonic Solution

Two solutions that exert the same osmotic pressure and have equal molar concentrations (e.g., $0.91\%$ pure $\text{NaCl}$ solution is isotonic with human RBCs).

Reverse Osmosis

The process occurring when external pressure higher than osmotic pressure is applied to a solution, forcing solvent to flow from the solution to pure solvent.

van 't Hoff Factor ($i$)

The ratio of the observed value of a colligative property to its calculated value, used to correct for solute association ($i < 1$) or dissociation ($i > 1$).

Degree of Dissociation ($\alpha$)

The fraction of total solute molecules that dissociate into ions or smaller particles, related to the van 't Hoff factor by $\alpha = \frac{i - 1}{n - 1}$.

Degree of Association ($\alpha$)

The fraction of total solute molecules that combine to form associated molecules, related to the van 't Hoff factor by $\alpha = \frac{1 - i}{1 - \frac{1}{n}}$.