General Chemistry II: Ch 11, 13, 16 (Exam 1)

Antibonding Molecular Orbital (Antibonding MO):

A molecular orbital formed by

destructive overlap of atomic orbitals. It has higher energy than the original atomic

orbitals, contains a node between the nuclei, and decreases the stability of the molecule.

Bonding Molecular Orbital (Bonding MO):

A molecular orbital formed by constructive

overlap of atomic orbitals. It has lower energy than the original atomic orbitals,

concentrates electron density between the nuclei, and stabilizes the molecule.

Homonuclear Diatomic Molecule:

A molecule composed of two atoms of the same

element. Examples: H₂, N₂, O₂, F₂.

Hybrid Orbital:

A new atomic orbital formed by mixing two or more atomic orbitals on

the same atom during bonding.

Hybridization: 

The process in which two or more atomic orbitals on the same atom

combine to form hybrid orbitals with specific shapes and orientations for bonding.

Molecular Orbital (MO) Bond Order: 

A measure of bond strength calculated from the

numbers of bonding and antibonding electrons.

Bond Order 

½(Bonding electrons−Antibonding electrons)

Higher bond order indicates a stronger and shorter bond.

Molecular Orbital (MO):

 An orbital that belongs to the entire molecule rather than to a

single atom and can contain electrons shared by all atoms in the molecule.

Molecular Orbital (MO) Diagram:

An energy-level diagram that shows the relative

energies of molecular orbitals and how electrons occupy them according to the Aufbau

principle, Pauli exclusion principle, and Hund's rule.

Molecular Orbital (MO) Theory: 

A quantum mechanical theory that explains chemical

bonding by treating electrons as occupying molecular orbitals that extend over the entire

molecule.

Nonbonding Molecular Orbital (Nonbonding MO):

A molecular orbital whose energy

is nearly the same as the original atomic orbital because it neither stabilizes nor

destabilizes the molecule.

Pi (π) Bond):

A covalent bond formed by the side-to-side overlap of parallel

unhybridized p orbitals. A π bond accompanies a σ bond in double and triple bonds.

Pi (π) Molecular Orbital (π MO): 

 A molecular orbital formed by the side-to-side overlap

of p atomic orbitals, with electron density above and below the bond axis.

Sigma (σ) Bond:

 A covalent bond formed by the end-to-end overlap of atomic or hybrid

orbitals along the line joining two nuclei. Every single bond is a σ bond.

Sigma (σ) Molecular Orbital (σ MO):

A molecular orbital formed by end-to-end overlap

of atomic orbitals, with electron density concentrated directly along the bond axis.

sp Hybrid Orbital:

A hybrid orbital formed by mixing one s orbital and one p orbital,

producing two equivalent orbitals arranged 180° apart. Associated geometry: Linear

sp² Hybrid Orbital: 

 A hybrid orbital formed by mixing one s orbital and two p orbitals,

producing three equivalent orbitals arranged 120° apart in a plane. Associated geometry:

Trigonal planar

sp³ Hybrid Orbital:

 A hybrid orbital formed by mixing one s orbital and three p orbitals,

producing four equivalent orbitals arranged tetrahedrally. Associated geometry:

Tetrahedral

sp³d Hybrid Orbital: 

 A hybrid orbital formed by mixing one s orbital, three p orbitals, and

one d orbital, producing five equivalent orbitals. Associated geometry: Trigonal

bipyramidal

sp³d² Hybrid Orbital:

A hybrid orbital formed by mixing one s orbital, three p orbitals,

and two d orbitals, producing six equivalent orbitals. Associated geometry: Octahedral

Valence Bond (VB) Theory:

A quantum mechanical theory that explains covalent

bonding as the overlap of atomic or hybrid orbitals on adjacent atoms, with the shared

electrons localized between the bonded atoms.

Activation energy (Ea) 

The minimum energy that reacting particles must possess for

a collision to result in a chemical reaction.

Active site 

The specific region of an enzyme where the substrate binds and the

catalyzed chemical reaction occurs.

Arrhenius equation 

An equation describing the dependence of the rate constant on

temperature and activation energy:

Average rate

The change in the concentration of a reactant or product divided by the

time interval over which the change occurs.

Bimolecular reaction 

 An elementary reaction involving the collision and reaction of

two reactant particles.

Catalyst 

A substance that increases the rate of a chemical reaction without

undergoing permanent chemical change or being consumed overall.

Chemical kinetics 

The study of reaction rates, the factors that affect reaction rates,

and the mechanisms by which chemical reactions occur.

Collision theory 

A theory stating that chemical reactions occur when reactant

particles collide with sufficient energy and the proper orientation.

Effective collision

A collision between reactant particles that has sufficient energy

and appropriate orientation to produce a chemical reaction.

Elementary reaction (elementary step) 

A single molecular event in a reaction

mechanism that occurs exactly as represented by its chemical equation.

Enzyme

A biological catalyst, usually a protein, that increases the rate of a

biochemical reaction without being permanently consumed.

Enzyme–substrate complex (ES) 

A temporary complex formed when a substrate

binds to the active site of an enzyme.

Frequency factor (A) 

The factor in the Arrhenius equation that accounts primarily for

collision frequency and the probability that reacting particles have the proper orientation

for reaction.

Half-life 

The time required for half of the amount of a reactant present at the

beginning of a time interval to be consumed.

Heterogeneous catalyst 

A catalyst that is in a different phase from the reactants.

The reaction generally occurs on the surface of the catalyst.

Homogeneous catalyst 

A catalyst that is in the same phase as the reactants and

participates temporarily in the reaction mechanism before being regenerated.

Hydrogenation

A reaction in which hydrogen is added to an unsaturated compound,

often using a metal catalyst such as nickel, palladium, or platinum.

Induced-fit model 

A model of enzyme action in which substrate binding causes a

change in the enzyme's shape, producing a better fit between the enzyme and substrate

and promoting the reaction.

Initial rate 

The reaction rate measured at or very near the beginning of a reaction,

before significant changes in reactant concentrations or product accumulation have

occurred.

Instantaneous rate 

The reaction rate at one specific moment in time. Graphically, it

is obtained from the slope of the tangent line to a concentration-versus-time curve at that

instant.

Integrated rate law

 An equation relating reactant concentration to time and the rate

constant.

 Lock-and-key model 

A model of enzyme action in which the active site has a fixed

shape that is complementary to the shape of the substrate.

Molecularity 

 The number of reactant particles involved in a single elementary

reaction. Elementary steps may be unimolecular, bimolecular, or, less commonly,

termolecular.

Rate constant (kkk)

 The proportionality constant in a rate law that relates reaction

rate to reactant concentrations. Its value depends primarily on temperature and the

specific reaction.

Rate-determining step (rate-limiting step) 

The slowest elementary step in a

multistep reaction mechanism. It acts as a bottleneck and controls the overall reaction

rate.

Rate law (rate equation) 

An experimentally determined equation that relates reaction

rate to reactant concentrations.

 Reaction energy diagram

A graph showing the potential energy of a reacting system

as it progresses from reactants through the transition state to products. It shows the

activation energy and overall energy change of the reaction.

 Reaction intermediate 

A species that is produced in one step of a reaction

mechanism and consumed in a later step. It does not appear in the overall balanced

reaction.

Reaction mechanism 

The sequence of elementary reactions through which an

overall chemical reaction occurs.

 Reaction order

The exponent of a reactant concentration in a rate law. The overall

reaction order is the sum of all concentration exponents in the rate law..

Reaction rate

A measure of how rapidly reactants are consumed or products are

formed, usually expressed as a change in molar concentration per unit time.

Substrate

A reactant molecule that binds to the active site of an enzyme and

undergoes a catalyzed chemical reaction.

Transition state (activated complex) 

 A temporary, high-energy arrangement of

atoms formed at the top of the activation-energy barrier. It can proceed toward products

or return to reactants.

Transition state theory 

 A theory of reaction rates based on the formation of a high-

energy activated complex or transition state between reactants and products.

Unimolecular reaction 

An elementary reaction in which a single reactant particle

undergoes a chemical transformation or decomposition.

Alloy

A solid solution composed of two or more elements, at least one of which is a

metal.

Boiling-point elevation (ΔTb ) 

The increase in the boiling point of a solvent caused

by dissolving a nonvolatile solute in it.

Charge density 

The amount of electric charge concentrated in a given region or

associated with the size of an ion. Smaller, more highly charged ions have greater

charge density.

 Colligative property 

 A property of a solution that depends on the concentration or

number of dissolved solute particles rather than their chemical identity. Examples are

vapor-pressure lowering, boiling-point elevation, freezing-point depression, and osmotic

pressure.

Colloid

A stable, nonhomogeneous mixture containing particles larger than those in a

true solution but small enough to remain dispersed rather than settling out.

Desalination

The removal of dissolved salts and other ions from seawater or

saltwater to produce water with a lower salt concentration.

Dipole-induced dipole force

An intermolecular attraction in which a polar molecule

distorts the electron distribution of a nonpolar molecule, temporarily creating a dipole.

Entropy (SS)

A thermodynamic quantity related to the dispersal of matter and energy

in a system.

Fractional distillation

A method for separating a mixture of liquids by repeated

cycles of evaporation and condensation, taking advantage of differences in their vapor

pressures or boiling points.

Freezing-point depression (ΔTf) 

The decrease in the freezing point of a solvent

caused by dissolving a solute in it.

Heat (enthalpy) of hydration (ΔHhydr ) 

The enthalpy change that occurs when

gaseous ions become surrounded and stabilized by water molecules.

Heat (enthalpy) of solution (ΔHsoln )

The overall enthalpy change that occurs when a

solute dissolves in a solvent.

Henry’s law 

The principle stating that, at constant temperature, the solubility of a gas

in a liquid is directly proportional to the partial pressure of that gas above the solution.

Hydration

The process in which dissolved solute particles, especially ions, become

surrounded by water molecules.

Hydration shell

The organized layer of water molecules surrounding and interacting

with a dissolved ion or polar particle.

Ideal solution

A solution in which the intermolecular interactions between unlike

molecules are approximately equal in strength to those between like molecules and each

volatile component obeys Raoult’s law.

Immiscible

Describes two liquids that do not mix appreciably to form a homogeneous

solution.

Ionic atmosphere

The region surrounding an ion in solution in which there is a

greater concentration of oppositely charged ions than similarly charged ions.

Ion-induced dipole force 

 An attraction that occurs when an ion distorts the electron

distribution of a nearby nonpolar molecule, creating a temporary dipole.

Like-dissolves-like rule 

The general guideline that substances dissolve most readily

in solvents with similar polarity and intermolecular forces: polar dissolves polar and

nonpolar dissolves nonpolar.

Mass percent [% (w/w)] 

The mass of solute divided by the total mass of the solution,

multiplied by 100%.

Miscible

 Describes two liquids that mix completely with one another in any proportion

to form a homogeneous solution.

Molality (m) 

The number of moles of solute per kilogram of solvent.

Mole fraction (X)

The number of moles of one component divided by the total

number of moles of all components in the mixture.

Nonelectrolyte

A substance that dissolves without forming ions and therefore

produces a solution that does not conduct electricity significantly.

Osmosis

The net movement of solvent through a semipermeable membrane from a

region of lower solute concentration toward a region of higher solute concentration.

Osmotic pressure (Π\PiΠ)

The pressure that must be applied to a solution to prevent

the net movement of solvent into it by osmosis.

Raoult’s law

 The principle stating that the vapor pressure of a solvent above an ideal

solution equals the mole fraction of the solvent multiplied by the vapor pressure of the

pure solvent.

Reverse osmosis 

A process in which pressure greater than the osmotic pressure is

applied to a solution, forcing solvent through a semipermeable membrane in the

direction opposite to normal osmosis.

Saturated solution

A solution containing the maximum amount of dissolved solute

possible at a particular temperature.

Semipermeable membrane

A barrier that allows solvent molecules to pass through

but prevents solute particles from passing.

Soap

A salt of a long-chain fatty acid whose ions contain a nonpolar hydrocarbon tail

and a polar or ionic head, allowing oily substances to disperse in water.

Solubility (SSS) 

The maximum amount of a solute that can dissolve in a given

quantity of solvent under specified conditions of temperature and pressure.

Solute

The component of a solution that is dissolved in the solvent and is generally

present in the smaller amount.

Solvation

The process in which solvent molecules surround and interact with

dissolved solute particles.

Solvent

The component of a solution that acts as the dissolving medium and is

generally present in the largest amount.

Strong electrolyte

A substance that dissociates or ionizes essentially completely into

ions when dissolved in water.

Supersaturated solution 

An unstable solution containing more dissolved solute than

is normally present in a saturated solution at the same temperature.

Suspension

A heterogeneous mixture containing relatively large particles that

eventually settle out of the dispersing medium.

Tyndall effect 

 The scattering of visible light by colloidal particles, making the path of

a light beam visible as it passes through a colloid.

 Unsaturated solution 

A solution containing less than the maximum amount of solute

that can dissolve at a given temperature, meaning that additional solute can still

dissolve.

Vapor-pressure lowering (ΔP\Delta PΔP)

The decrease in a solvent’s vapor

pressure caused by the presence of a dissolved solute.

Volume percent [% (v/v)] 

The volume of solute divided by the total volume of the

solution, multiplied by 100%.

Weak electrolyte

A substance that only partially ionizes in water, producing a mixture

of ions and un-ionized molecules in solution.