General Chemistry: Reactions in Aqueous Solution, Gases, and Thermochemistry

Comprehensive vocabulary flashcards covering chemical reaction classes, solution stoichiometry, gas laws, kinetic-molecular theory, and thermochemical principles.

Criss-Cross Method

A technique used to determine the subscripts in an ionic formula by crossing over the numerical charges of the cation and anion to become the opposite ion's subscript, ensuring the net charge balances to zero.

Empirical Formula

A chemical formula that represents the simplest whole-number ratio of the different atoms present in a compound.

Molecular Formula

A chemical formula that indicates the actual number of atoms of each element in a single molecule of a compound.

Single Displacement Reaction

A reaction where a free element displaces an ion from a compound ($A + BC \rightarrow AC + B$); it proceeds only if the free element is more reactive than the element it replaces based on the activity series.

Double Displacement Reaction

A reaction in which two aqueous ionic compounds exchange ionic partners ($AB + CD \rightarrow AD + CB$), occurring only if driven by the formation of an insoluble precipitate, a gas, or water.

Molarity ($M$)

A unit of solution concentration defined as the number of moles of solute divided by the volume of solution in liters ($\text{Molarity} = \frac{n}{V}$).

Dilution Formula

The relationship $M_1V_1 = M_2V_2$, used to calculate the volume of concentrated stock solution required to prepare a specific volume and concentration of a more dilute solution.

Precipitation Reaction

A reaction in which soluble aqueous ions combine to form an insoluble solid crystal, known as a precipitate.

Net Ionic Equation

A chemical equation written by eliminating spectator ions from a complete ionic equation to show only the species undergoing the actual chemical transformation.

Spectator Ions

Ions that remain unchanged on both the reactant and product sides of a reaction and do not participate directly in the chemical change.

Strong Electrolyte

A substance that dissociates completely into ions when dissolved in water, producing a solution that conducts electricity efficiently.

Weak Electrolyte

A substance that dissociates only partially into ions in aqueous solution, resulting in poor electrical conductivity.

Nonelectrolyte

A molecular substance that dissolves in water as intact neutral molecules without forming ions, resulting in a solution that does not conduct electricity.

Arrhenius Acid

A substance that produces hydrogen ions ($H^+$) when dissolved in water.

Arrhenius Base

A substance that produces hydroxide ions ($OH^-$) when dissolved in water.

Hydronium Ion ($H_3O^+$)

The species formed when a free hydrogen ion ($H^+$) strongly bonds to a water molecule in aqueous solution ($H^+ + H_2O \rightarrow H_3O^+$).

Equivalence Point

The exact point in an acid-base titration where the moles of $H^+$ from the acid are stoichiometrically equal to the moles of $OH^-$ delivered by the base.

End Point

The point in a titration where an added indicator permanently changes color, typically reflecting a slight excess of titrant.

Dynamic Equilibrium

A state in a reversible process where the rates of the forward and reverse reactions are equal, causing macroscopic concentrations to remain unchanged over time.

Oxidation

The chemical process involving the loss of electrons, which leads to an increase in oxidation number.

Reduction

The chemical process involving the gain of electrons, which leads to a decrease in oxidation number.

Reducing Agent

The reactant that donates electrons and is oxidized, thereby causing the reduction of another chemical species.

Oxidizing Agent

The reactant that accepts electrons and is reduced, thereby causing the oxidation of another chemical species.

Activity Series of the Metals

A ranking of metallic elements from strongest reducing agent to weakest reducing agent, determining their ability to displace hydrogen gas from liquid water, steam, or acids.

Boyle’s Law

The gas law stating that at constant temperature and mole quantity, gas pressure is inversely proportional to volume ($P_1V_1 = P_2V_2$).

Charles’s Law

The gas law stating that at constant pressure and mole quantity, gas volume is directly proportional to its absolute temperature ($\frac{V_1}{T_1} = \frac{V_2}{T_2}$).

Amonton’s Law

The gas law stating that at constant volume and mole quantity, gas pressure is directly proportional to absolute temperature ($\frac{P_1}{T_1} = \frac{P_2}{T_2}$).

Avogadro’s Law

The gas law stating that at constant temperature and pressure, gas volume is directly proportional to the amount of gas in moles ($\frac{V_1}{n_1} = \frac{V_2}{n_2}$).

Ideal Gas Law

The unified equation of state $PV = nRT$, describing the relationship between pressure, volume, amount in moles, the universal gas constant, and absolute temperature.

Standard Temperature and Pressure (STP)

A standard reference condition defined historically as $0\,^\circ\text{C}$ ($273.15\,\text{K}$) and $1\,\text{atm}$ ($22.4\,\text{dm}^3\,\text{mol}^{-1}$ molar volume), or in modern usage as $0\,^\circ\text{C}$ and $1\,\text{bar}$ ($22.7\,\text{dm}^3\,\text{mol}^{-1}$ molar volume).

Dalton’s Law of Partial Pressures

The law stating that the total pressure of a mixture of nonreacting gases is equal to the sum of the partial pressures exerted by each individual gas component ($P_{\text{total}} = P_1 + P_2 + P_3 + \dots$).

Mole Fraction ($X$)

The dimensionless ratio of the number of moles of a specific substance in a mixture to the total number of moles of all substances present ($X_1 = \frac{n_1}{n_{\text{total}}}$).

Root-Mean-Square Speed ($u_{\text{rms}}$)

The speed of a gas particle with kinetic energy equal to the sample's average kinetic energy, given by $u_{\text{rms}} = \sqrt{\frac{3RT}{M}}$, where molar mass $M$ must be expressed in $\text{kg}\,\text{mol}^{-1}$.

Effusion

The movement of gas particles escaping from an enclosed container into an evacuated space through a tiny pinhole aperture.

Graham’s Law of Effusion

The principle stating that the rate of gas effusion is inversely proportional to the square root of the gas's molar mass ($\frac{\text{Rate}_A}{\text{Rate}_B} = \sqrt{\frac{M_B}{M_A}}$).

Diffusion

The gradual mixing of one gaseous substance throughout another driven by continuous, random particle motion and collisions.

Deviations from Ideal Gas Behavior

The departures from ideal behavior observed at low temperatures and high pressures, caused by significant interparticle attractive forces ($\frac{PV}{RT} < 1$) and finite particle volume ($\frac{PV}{RT} > 1$).

Van der Waals Equation

An equation of state modified for real gases, $\left(P + \frac{n^2 a}{V^2}\right)(V - nb) = nRT$, where $a$ corrects for intermolecular attractions and $b$ corrects for molecular volume.

Barometer

A laboratory instrument that measures atmospheric pressure using the height of a supported mercury column.

Manometer

A device used to measure the internal pressure of an enclosed gas sample relative to atmospheric pressure or a vacuum.

Thermochemistry

The branch of thermodynamics that investigates the heat energy exchanged during chemical reactions and physical phase changes.

System and Surroundings

The system is the designated matter under study (such as the reactants and products inside a reaction flask), while the surroundings encompass everything else outside the system boundary.

First Law of Thermodynamics

The principle of energy conservation stating that energy cannot be created or destroyed, meaning the total energy change of the universe is zero ($\Delta E_{\text{universe}} = \Delta E_{\text{system}} + \Delta E_{\text{surroundings}} = 0$).

Internal Energy ($E$)

The total sum of all microscopic kinetic and potential energies possessed by the particles comprising a thermodynamic system.

Pressure-Volume Work ($w$)

The work resulting from the expansion or compression of a gas volume against external pressure, calculated as $w = -P\Delta V$.

Enthalpy ($H$)

A state function defined as internal energy plus the product of pressure and volume ($H = E + PV$), whose change ($\Delta H$) equals heat transferred at constant pressure ($q_p$).

Exothermic Process

A process that releases thermal energy to its surroundings, characterized by a negative enthalpy change ($\Delta H < 0$).

Endothermic Process

A process that absorbs thermal energy from its surroundings, characterized by a positive enthalpy change ($\Delta H > 0$).

Specific Heat Capacity ($c$)

The amount of heat energy required to raise the temperature of exactly $1\,\text{g}$ of a substance by $1\,\text{K}$ (or $1\,^\circ\text{C}$), with units of $\text{J}/(\text{g}\cdot\text{K})$ or $\text{J}/(\text{g}\cdot^\circ\text{C})$.

Molar Heat Capacity ($c_m$)

The amount of heat energy required to raise the temperature of exactly $1\,\text{mol}$ of a substance by $1\,\text{K}$.

Heat Capacity ($C$)

The amount of heat energy needed to raise the temperature of an entire object or experimental calorimeter assembly by $1\,\text{K}$, expressed in units of $\text{J}\,\text{K}^{-1}$.

Coffee-Cup Calorimeter

A nested-cup constant-pressure device used to determine heat changes for reactions in solution by assuming $q_{\text{cal}} = -q_{\text{rxn}}$, where $q_{\text{cal}} = (m \cdot c \cdot \Delta T)_{\text{solution}}$.

Bomb Calorimeter

A rigid, constant-volume calorimeter used to measure heats of combustion according to $q_{\text{cal}} = C_{\text{cal}} \times \Delta T_{\text{cal}} = -q_{\text{rxn}}$.

Hess’s Law

The principle stating that if a reaction is carried out in a series of steps, the overall enthalpy change is the sum of the enthalpy changes for each individual step ($\Delta H_{\text{overall}} = \Delta H_1 + \Delta H_2 + \Delta H_3 + \dots$).

Standard Enthalpy of Formation ($\Delta H^\circ_f$)

The enthalpy change occurring when exactly $1\,\text{mol}$ of a substance is synthesized from its constituent elements in their standard reference states at $1\,\text{atm}$ and $25\,^\circ\text{C}$.

Standard State of Pure Elements Rule

The thermodynamic convention dictating that the standard heat of formation ($\Delta H^\circ_f$) for any pure element in its most stable physical state at $1\,\text{atm}$ and $25\,^\circ\text{C}$ is defined as exactly $0\,\text{kJ}\,\text{mol}^{-1}$.