Chemistry: Intermolecular Forces, Solutions, and Chemical Kinetics

Vocabulary flashcards generated from lecture materials covering intermolecular forces, properties of liquids, solutions and colligative properties, and chemical kinetics.

Intermolecular Forces

Attractions and repulsions between neighboring particles (atoms, molecules, or ions) that hold solids and liquids together, distinct from intramolecular chemical bonds.

Intramolecular Forces

Chemical bonding forces (such as ionic and covalent bonds) within a molecule that govern molecular stability and chemical properties.

Ion-Dipole Forces

Intermolecular electrostatic interactions occurring between an ion and the partial charges of a permanent dipole on a polar molecule, with strengths typically ranging from $10\text{--}50\text{ kJ/mol}$.

Dipole-Dipole Forces

Intermolecular attractions resulting from electrical interactions between permanent dipoles on adjacent polar molecules, with strengths typically ranging from $3\text{--}4\text{ kJ/mol}$.

London Dispersion Forces

Weak intermolecular forces ($1\text{--}10\text{ kJ/mol}$) present between all particles, caused by temporary fluctuations in electron density that induce temporary dipoles in adjacent molecules.

Polarizability

The measure of the ease with which the electron cloud of an atom or molecule can be distorted by an external electrical charge or neighboring dipole.

Hydrogen Bond

A moderate attractive force ($10\text{--}40\text{ kJ/mol}$) between a hydrogen atom bonded to a highly electronegative atom ($\text{N}$, $\text{O}$, or $\text{F}$) and a lone pair on a neighboring electronegative atom.

Viscosity

The quantitative measure of a liquid's internal resistance to flow.

Surface Tension

The energy required to increase the surface area of a liquid, caused by the unbalanced inward attractive forces experienced by surface molecules.

Equilibrium Vapor Pressure

The pressure exerted by a vapor in dynamic equilibrium with its liquid phase in a closed container at a given temperature, where rate of evaporation equals rate of condensation.

Critical Point

The specific combination of critical temperature and critical pressure beyond which distinct liquid and gas phases cease to exist.

Critical Temperature

The temperature above which a gas cannot be liquefied, regardless of the magnitude of the applied pressure.

Supercritical Fluid

A high-density state of matter formed beyond the critical point that exhibits properties of both liquids and gases.

Triple Point

The unique condition of temperature and pressure at which solid, liquid, and gas phases of a substance coexist in dynamic equilibrium.

Enthalpy of Fusion ($\Delta H_{\text{fusion}}$)

The amount of energy required to convert a given quantity of a solid into its liquid state at its melting point.

Enthalpy of Vaporization ($\Delta H_{\text{vap}}$)

The amount of energy required to convert a given quantity of a liquid into its gaseous state at its boiling point.

Clausius-Clapeyron Equation

An equation expressing the logarithmic relationship between the vapor pressure of a liquid and temperature: $\ln(P_{\text{vap}}) = -\frac{\Delta_{\text{vap}}H^\circ}{RT} + C$.

Solution

A homogeneous mixture composed of two or more substances single-phased throughout.

Solvent

The component of a solution present in the largest quantitative amount.

Solute

The minor component dissolved within a solvent to form a solution.

Molarity ($M$)

A concentration unit defined as the number of moles of solute dissolved per liter of solution ($\text{mol/L}$).

Molality ($m$)

A temperature-independent concentration unit defined as the number of moles of solute per kilogram of solvent ($\text{mol/kg}$).

Mole Fraction ($X$)

A dimensionless concentration expression defined as the ratio of moles of a specific component to the total moles of all components in a solution.

Parts Per Million (ppm)

A concentration measure calculated as $\frac{\text{mass of solute}}{\text{mass of solution}} \times 10^6$.

Saturated Solution

A solution that contains the maximum concentration of dissolved solute in dynamic equilibrium with undissolved solute.

Supersaturated Solution

An unstable solution containing a greater amount of dissolved solute than present at thermodynamic equilibrium.

Henry's Law

A relationship stating that the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid ($\text{Solubility} = k \times P$).

Colligative Properties

Physical properties of solutions that depend solely on the total concentration of solute particles, regardless of their chemical identity.

Raoult's Law

A principle stating that the partial vapor pressure of a solvent above a solution is equal to the vapor pressure of pure solvent multiplied by its mole fraction: $P_{\text{soln}} = P_{\text{solv}} \times X_{\text{solv}}$.

van 't Hoff Factor ($i$)

The ratio of moles of dissolved particles in solution to moles of solute formula units initially dissolved.

Osmosis

The spontaneous net passage of solvent molecules through a semipermeable membrane from a solution of lower solute concentration to one of higher solute concentration.

Osmotic Pressure ($\Pi$)

The pressure required to stop osmotic solvent flow across a semipermeable membrane, given by $\Pi = iMRT$.

Chemical Kinetics

The area of chemistry concerned with measuring reaction rates and elucidating the sequence of elementary steps in reaction mechanisms.

Reaction Rate

The positive change in product concentration per unit time or the negative change in reactant concentration per unit time.

Rate Law

An experimentally determined equation relating the rate of a chemical reaction to the rate constant ($k$) and reactant concentrations raised to specific powers.

Rate Constant ($k$)

A temperature-dependent proportionality constant in the rate law expression specific to a given reaction.

Half-Life ($t_{1/2}$)

The time period required for the concentration of a reactant to decrease to exactly one-half of its initial value.

Reaction Mechanism

The step-by-step sequence of individual elementary reactions that describes the precise molecular path from reactants to products.

Elementary Reaction

A single, discrete step in a reaction mechanism that describes an individual molecular collision or event.

Reactive Intermediate

A chemical species produced in an early elementary step of a mechanism and consumed in a subsequent step, not appearing in the overall balanced equation.

Molecularity

The total number of reactant molecules, atoms, or ions coming together in a single elementary reaction step.

Rate-Determining Step

The slowest elementary step in a reaction mechanism, which acts as a bottleneck and dictates the overall reaction rate law.

Activation Energy ($E_a$)

The minimum threshold energy colliding reactant molecules must possess for a reaction to occur.

Transition State

The transient, high-energy arrangement of atoms formed at the peak of the potential energy barrier during a chemical reaction, also called the activated complex.

Arrhenius Equation

An equation expressing the mathematical dependence of the rate constant on temperature and activation energy: $k = A e^{-E_a/RT}$.

Catalyst

A substance that accelerates a chemical reaction by offering an alternative pathway with lower activation energy without being permanently consumed.

Homogeneous Catalyst

A catalyst present in the same physical phase as the reacting species.

Heterogeneous Catalyst

A catalyst present in a different physical phase from the reacting species, typically a solid catalyst in a liquid or gaseous reaction mixture.