FY13CE Chemistry flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Atomic number

The number of protons in an atom's nucleus; it defines the element and equals the number of electrons in a neutral atom.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons, giving different mass numbers but identical chemical behavior.

First ionization energy

The energy required to remove one mole of electrons from one mole of gaseous atoms; it generally increases across a period and decreases down a group.

Electron configuration exception

Chromium and copper adopt [Ar]3d5 4s1 and [Ar]3d10 4s1 because half-filled and fully filled d subshells provide extra stability.

VSEPR theory

Electron domains around a central atom repel each other and arrange to maximize separation, determining molecular geometry from the number of bonding and lone pairs.

Hybridization

The mixing of atomic orbitals to form equivalent hybrid orbitals; sp is linear, sp² trigonal planar, and sp³ tetrahedral, matching observed bond angles.

Polar covalent bond

A bond in which electrons are shared unequally because the atoms differ in electronegativity, creating partial positive and negative charges on the atoms.

Bond order

Half the difference between bonding and antibonding electrons in molecular orbital theory; higher bond order means a shorter and stronger bond.

Hydrogen bond

A strong dipole attraction between a hydrogen bonded to N, O, or F and a lone pair on another electronegative atom, raising boiling points notably.

Ideal gas law

PV = nRT relates pressure, volume, moles, and absolute temperature; R is 0.08206 L atm mol⁻¹ K⁻¹ or 8.314 J mol⁻¹ K⁻¹.

Critical temperature

The highest temperature at which a substance can exist as a liquid; above it, pressure alone cannot liquefy the gas.

Limiting reactant

The reactant that is completely consumed first and therefore determines the maximum amount of product that can form in a reaction.

Molarity

The concentration of a solution expressed as moles of solute per liter of solution; dilution follows M1V1 = M2V2.

Percent yield

The actual yield of product divided by the theoretical yield predicted from stoichiometry, multiplied by 100 to give a percentage.

Hess's law

The enthalpy change of an overall reaction equals the sum of the enthalpy changes of its steps, because enthalpy is a state function.

Standard enthalpy of formation

The enthalpy change when one mole of a compound forms from its elements in their standard states; elements in standard states have zero value.

Gibbs free energy

ΔG = ΔH − TΔS determines spontaneity: negative ΔG means spontaneous, zero means equilibrium, and positive means nonspontaneous.

Activation energy

The minimum energy reactants must possess to form products; a catalyst lowers it, increasing reaction rate without changing the enthalpy change.

First-order half-life

For a first-order reaction, the time for reactant concentration to halve is 0.693/k, independent of the starting concentration.

Le Chatelier's principle

When a system at equilibrium is disturbed by concentration, pressure, or temperature change, it shifts to partially offset that disturbance.

Equilibrium constant

Kc is the ratio of product concentrations to reactant concentrations, each raised to its stoichiometric coefficient, at equilibrium; pure solids and liquids are excluded.

pH

pH = −log[H⁺]; values below 7 are acidic, 7 neutral, and above 7 basic at 25 °C where pH + pOH = 14.

Buffer solution

A mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid, that resists pH change on adding small amounts of acid or base.

Equivalence point

The point in a titration where the moles of added titrant exactly match the stoichiometric amount required to react with the analyte.

Oxidation

The loss of electrons by a species, corresponding to an increase in oxidation number; oxidation occurs at the anode of an electrochemical cell.

Standard cell potential

E°cell = E°cathode − E°anode; a positive value indicates a spontaneous galvanic reaction under standard conditions.

Amphoteric oxide

An oxide that reacts with both acids and bases to form salts, such as aluminum oxide and zinc oxide.

Halogen reactivity trend

Halogen oxidizing strength decreases down group 17 as atomic radius and shielding increase, so fluorine is the strongest and iodine the weakest.

Esterification

The acid-catalyzed reaction of a carboxylic acid with an alcohol to form an ester and water, often called Fischer esterification.

Tollens' test

A mild oxidation test using silver nitrate in ammonia; aldehydes reduce it to a silver mirror, while ketones do not react.

Chromatography

A separation technique in which components move at different rates between a mobile phase and a stationary phase because of differing affinities.

Beer–Lambert law

A = εbc states that absorbance is proportional to concentration and path length, enabling quantitative analysis by spectrophotometry.