General Chemistry: Thermochemistry, Electronic Structure, and Aqueous Reactions

Comprehensive vocabulary flashcards covering Thermochemistry (Chapter 5), Electronic Structure of Atoms (Chapter 6), and Reactions in Aqueous Solution (Chapter 4) from Chemistry: The Central Science.

Thermochemistry

The study of chemical reactions and the energy changes that involve heat.

Electrostatic Potential Energy ($E_{el}$)

The most important form of potential energy in molecules, proportional to the product of charges and inversely proportional to the separation distance: $E_{el} = \frac{k Q_1 Q_2}{d}$.

Joule ($\text{J}$)

The commonly used unit of energy, defined as $1\,\text{J} = 1\,\frac{\text{kg}\,\text{m}^2}{\text{s}^2}$.

First Law of Thermodynamics

The principle stating that energy can be converted from one form to another, but it is neither created nor destroyed.

System

The specific portion of the universe that is singled out for thermodynamic study.

Surroundings

Everything in the universe outside the thermodynamic system being studied.

Open System

A region of the universe being studied that can exchange both heat and mass with its surroundings.

Closed System

A region of the universe being studied that can exchange heat with its surroundings, but cannot exchange mass.

Isolated System

A region of the universe that cannot exchange either heat or mass with its surroundings.

Internal Energy ($E$)

The sum of all kinetic and potential energies of all components of a system.

Endothermic Process

A process in which heat is absorbed by the system from the surroundings, resulting in $q > 0$ and $\Delta H > 0$.

Exothermic Process

A process in which heat is released by the system into the surroundings, resulting in $q < 0$ and $\Delta H < 0$.

State Function

A property of a system that depends only on its present state and is independent of the path by which the system arrived at that state.

Pressure-Volume Work

Mechanical work performed by or on a system when gas volume changes under external pressure, given by $w = -P\Delta V$.

Enthalpy ($H$)

A thermodynamic property defined as $H = E + PV$; at constant pressure, the change in enthalpy ($\Delta H$) equals the heat ($q$) gained or lost by the system.

Enthalpy of Reaction ($\Delta H_{rxn}$)

The enthalpy change of a chemical process, calculated as the enthalpy of the products minus the enthalpy of the reactants: $\Delta H_{rxn} = H_{\text{products}} - H_{\text{reactants}}$.

Constant-Pressure Calorimeter

A simple apparatus (such as nested Styrofoam cups with a stopper, stirrer, and thermometer) used to measure enthalpy changes of aqueous reactions at constant atmospheric pressure.

Bomb Calorimeter

A sealed, constant-volume combustion vessel surrounded by water, used to measure the change in internal energy ($\Delta E$) of a reaction via $q_{rxn} = -C_{cal} \times \Delta T$.

Heat Capacity

The amount of energy required to raise the temperature of an entire substance by $1\,\text{K}$ ($1\,^\circ\text{C}$).

Specific Heat ($C_s$)

The amount of energy required to raise the temperature of one gram of a substance by $1\,\text{K}$; for water, this is $4.184\,\text{J}/(\text{g}\cdot\text{K})$.

Hess's Law

The law stating that if a reaction is carried out in a series of steps, $\Delta H$ for the overall reaction equals the sum of the enthalpy changes for the individual steps.

Standard Enthalpy of Formation ($\Delta H_f^\circ$)

The enthalpy change for the reaction in which one mole of a compound is formed from its constituent elements in their elemental forms under standard conditions ($25\,^\circ\text{C}$ and $1.00\,\text{atm}$).

Bond Enthalpy

The enthalpy associated with breaking one mole of a particular chemical bond in a gaseous substance, which is always positive.

Fuel Value

The energy released when one gram of a food or fuel substance is combusted.

Electronic Structure

The arrangement and energy distribution of electrons in an atom.

Wavelength ($\lambda$)

The distance between corresponding points on adjacent waves, such as crest to crest or trough to trough.

Frequency ($\nu$)

The number of complete waves passing a given reference point per unit of time (measured in $\text{s}^{-1}$ or $\text{Hz}$).

Speed of Light ($c$)

The velocity at which all electromagnetic radiation travels in a vacuum, equal to $3.00 \times 10^8\,\text{m/s}$, defined by $c = \lambda\nu$.

Quanta

The discrete packets of energy postulated by Max Planck, representing the smallest indivisible units of energy emission or absorption.

Photoelectric Effect

The emission of electrons from a metal surface when light of a frequency exceeding a characteristic threshold shines upon it.

Planck's Constant ($h$)

The fundamental physical constant relating energy and frequency ($E = h\nu$), with an exact value of $6.626 \times 10^{-34}\,\text{J}\cdot\text{s}$.

Line Spectrum

A spectrum containing radiation of only discrete, specific wavelengths emitted or absorbed by excited atoms, unique to each element.

Ground State

The lowest possible energy state of an electron or atomic system.

Excited State

Any allowed energy state of an electron or atomic system that has higher energy than its ground state.

De Broglie Wavelength

The wave property exhibited by matter, relating wavelength to mass and velocity by $\lambda = \frac{h}{mv}$.

Heisenberg Uncertainty Principle

The principle stating that it is impossible to know simultaneously and with arbitrary precision both the momentum and position of a subatomic particle: $(\Delta x)(\Delta mv) \ge \frac{h}{4\pi}$.

Electron Density ($\psi^2$)

The probability of finding an electron at any given position in space, represented mathematically by the square of the wave function.

Principal Quantum Number ($n$)

The quantum number ($n = 1, 2, 3, \dots$) designating the main electron shell and primary energy level of an orbital.

Angular Momentum Quantum Number ($l$)

The quantum number defining orbital shape, having allowed integer values from $0$ to $n - 1$ ($0 = s$, $1 = p$, $2 = d$, $3 = f$).

Magnetic Quantum Number ($m_l$)

The quantum number describing the spatial orientation of an orbital in three dimensions, taking integer values from $-l$ to $+l$.

Node

A point or surface region in an orbital where the wave function passes through zero and the probability of finding an electron is zero.

d Orbitals

A set of five orbitals characterized by $l = 2$; four display four-lobed geometries ($d_{yz}, d_{xz}, d_{xy}, d_{x^2-y^2}$) and one displays a two-lobed geometry surrounded by a doughnut-shaped ring ($d_{z^2}$).

Degenerate Orbitals

Orbitals that reside at the exact same energy level.

Spin Quantum Number ($m_s$)

The quantum number describing the intrinsic magnetic orientation (spin) of an electron, taking values of only $+\frac{1}{2}$ or $-\frac{1}{2}$.

Pauli Exclusion Principle

The quantum mechanical rule stating that no two electrons within the same atom can possess identical sets of all four quantum numbers ($n, l, m_l, m_s$).

Hund's Rule

The principle stating that when filling degenerate orbitals, lowest energy is attained when the number of electrons having the same spin is maximized, placing one electron in each orbital before pairing.

Core Electrons

The electrons occupying inner, completely filled electron shells and completed $d$ or $f$ subshells of an atom.

Valence Electrons

The outermost electrons of an atom that occupy the highest principal energy level and participate in chemical bonding.

Solvation

The clustering and stabilization of solvent molecules around individual solute particles during the dissolving process.

Dissociation

The process by which solid ionic compounds break apart into separated, mobile aqueous ions when dissolved in water.

Electrolyte

A substance that dissolves in water to produce an electrically conducting solution containing dissolved ions.

Nonelectrolyte

A substance that dissolves in water to yield a solution of intact neutral molecules that does not conduct electricity.

Strong Electrolyte

A solute that dissociates or ionizes essentially completely into ions when dissolved in water.

Weak Electrolyte

A solute that ionizes only partially in water, establishing a dynamic chemical equilibrium between un-ionized molecules and ions.

Chemical Equilibrium

A dynamic state in a reversible reaction where the forward and reverse reactions proceed at equal rates, resulting in no net change in reactant and product amounts.

Precipitate

An insoluble solid product that separates from solution during a chemical reaction.

Metathesis Reaction

A reaction in aqueous solution where positive and negative ions appear to swap or transpose bonding partners.

Complete Ionic Equation

A chemical equation in which all dissolved strong electrolytes are depicted explicitly as separated, free ions.

Spectator Ions

Ions present in an aqueous reaction mixture that do not participate in the chemical transformation and appear unchanged on both sides of the reaction equation.

Net Ionic Equation

A simplified chemical equation obtained by eliminating spectator ions, leaving only the species directly involved in chemical reaction.

Acid

A substance that ionizes in aqueous solution to generate hydrogen ions ($\text{H}^+$), functioning as a proton donor.

Base

A substance that accepts $\text{H}^+$ ions or increases the concentration of hydroxide ions ($\text{OH}^-$) when dissolved in water.

Neutralization Reaction

A chemical reaction between an acid and a base, which, when involving a metal hydroxide base, generates water and a salt.

Salt

An ionic compound whose cation originates from a base and whose anion originates from an acid.

Oxidation

The thermodynamic or electrochemical process in which an atom, ion, or molecule loses electrons, increasing its oxidation number.

Reduction

The thermodynamic or electrochemical process in which an atom, ion, or molecule gains electrons, decreasing its oxidation number.

Oxidation Number

A positive or negative whole-number charge assigned to an atom according to a set of bookkeeping rules to track electron distribution.

Activity Series

A ranked listing of metals in order of decreasing ease of oxidation (reactivity) in aqueous solutions.

Molarity ($M$)

A quantitative concentration unit expressing the number of moles of solute dissolved per liter of solution: $\text{Molarity} = \frac{\text{moles of solute}}{\text{volume of solution in liters}}$.

Titration

An analytical laboratory method used to determine the unknown concentration of a solute in a solution by delivering a standard solution of known concentration via a burette.

Standard Solution

A reagent solution of accurately known concentration used in chemical titrations.

Equivalence Point

The exact point in a titration where the quantity of added titrant is stoichiometrically equivalent to the amount of substance present in the analyte.