Flashcards Midterm 2 Aleks Terms

Absolute Zero

Theoretically the lowest attainable temperature (0 K or −273.15°C ).

Avogadro's Law

The gas law stating that, at fixed temperature and pressure, equal volumes of any ideal gas contain equal numbers of particles, and, therefore, the volume of a gas is directly proportional to its amount (mol):V∝n.

Barometer

A device used to measure atmospheric pressure. Most commonly, a tube open at one end, which is filled with mercury and inverted into a dish of mercury.

Boyle's Law

The gas law stating that, at constant temperature and amount of gas, the volume occupied by a gas is inversely proportional to the applied (external) pressure:V∝ 1/P.

Charle's Law

The gas law stating that, at constant pressure, the volume occupied by a fixed amount of gas is directly proportional to its absolute temperature:V∝T.

Collision Frequency

The average number of collisions per second that a particle undergoes.

Dalton's Law of Partial Pressures

A gas law stating that, in a mixture of unreacting gases, the total pressure is the sum of the partial pressures of the individual gases:Ptotal =P1 +P2 +P3 + ⋅⋅⋅.

Diffusion

The movement of one fluid through another.

Effusion

The process by which a gas escapes from its container through a tiny hole into an evacuated space.

Graham's law of effusion

A gas law stating that the rate of effusion of a gas is inversely proportional to the square root of its density (or molar mass): rate proportional to 1/sqrM

Ideal gas

A hypothetical gas that exhibits linear relationships among volume, pressure, temperature, and amount (mol) at all conditions; approximated by simple gases at ordinary conditions.

Ideal Gas Law

(alsoideal gas equation) An equation that expresses the relationships among volume, pressure, temperature, and amount (mol) of an ideal gas:PV=nRT.

Kinetic-Molecular theory

The model that explains macroscopic gas behavior in terms of particles in random motion whose volumes and interactions are negligible.

Manometer

A device used to measure the pressure of a gas in a laboratory experiment.

Mean free path

The average distance a particle travels between collisions at a given temperature and pressure.

Millimeter of mercury (mmHg)

A unit of pressure based on the difference in the heights of mercury in a barometer or manometer. Renamed thetorrin honor of Torricelli.

Mole Fraction (X)

A concentration term expressed as the ratio of number of moles of solute to the total number of moles (solute plus solvent).

Partial Pressure

The portion of the total pressure contributed by a gas in a mixture of gases.

Pascal (Pa)

The SI unit of pressure; 1 Pa = 1 N/m2.

Pressure (P)

The force exerted per unit of surface area.

rms (root-mean-square) speed (urms)

The speed of a molecule having the average kinetic energy; very close to the most probable speed.

Standard atmosphere (atm)

The average atmospheric pressure measured at sea level and 0°C, defined as 1.01325 × 105 Pa.

Standard Molar Volume

The volume of 1 mol of an ideal gas at standard temperature and pressure: 22.4141 L.

Standard temperature and pressure

The reference conditions for a gas: 0°C (273.15 K) and 1 atm (760 torr).

Torr

A unit of pressure identical to 1 mmHg.

Universal Gas Constant (R)

A proportionality constant that relates the energy, amount of substance, and temperature of a system;R= 0.0820578 atm·L/mol·K = 8.31447 J/mol·K.

van der Waals constants

Experimentally determined positive numbers used in the van der Waals equation to account for the interparticle attractions and particle volume of real gases.

van der Waals equation

An equation that accounts for the behavior of real gases.

calorie (cal)

A unit of energy defined as exactly 4.184 joules; originally defined as the heat needed to raise the temperature of 1 g of water 1°C (from 14.5°C to 15.5°C).

calorimeter

A device used to measure the heat released or absorbed by a physical or chemical process taking place within it.

change in enthalpy (ΔH)

The change in the system's internal energy plus the product of the constant pressure and the change in volume: ΔH= ΔE+PΔV; alternatively, the heat lost or gained at constant pressure: ΔH=qP.

endothermic process

A process that occurs with an absorption of heat from the surroundings and therefore an increase in the enthalpy of the system (ΔH> 0).

formation equation

An equation in which 1 mole of a compound forms from its elements.

heat (q)

(alsothermal energy) The energy transferred between objects because of a difference in their temperatures only.

heat capacity (C)

The quantity of heat required to change the temperature of an object by 1 K.

Hess's Law

A law stating that the enthalpy change of an overall process is the sum of the enthalpy changes of the individual steps.

Internal Energy (E)

The sum of the kinetic and potential energies of all the particles in a system.

joule (J)

The SI unit of energy; 1 J = 1 kg·m2/s2.

law of conservation of energy

(alsofirst law of thermodynamics) A basic observation that the total energy of the universe is constant; thus, ΔEuniverse = ΔEsystem + ΔEsurroundings = 0.

molar heat capacity (Cm)

The quantity of heat required to change the temperature of 1 mol of a substance by 1 K.

pressure volume work

A type of mechanical work done when a volume change occurs against an external pressure.

specific heat capacity (c)

The quantity of heat required to change the temperature of 1 gram of a substance or material by 1 K.

standard enthalpy of formation (ΔH°f)

(alsostandard heat of formation) The enthalpy change occurring when 1 mol of a compound forms from its elements with all components in their standard states.

standard enthalpy of reaction (ΔH°rxn)

(alsostandard heat of reaction) The enthalpy change that occurs during a reaction when all components are in their standard states.

standard state

A set of specific conditions used to compare thermodynamic data: 1 atm for gases behaving ideally, 1Mfor dissolved species, or the pure substance for liquids and solids.

state function

A property of a system determined only by the system's current state, regardless of how it arrived at that state.

surroundings

All parts of the universe other than the system being considered.

system

The defined part of the universe under study.

thermochemical equation

A balanced chemical equation that includes the enthalpy change for the reaction.

thermochemistry

The branch of thermodynamics that focuses on the heat involved in chemical and physical change.

thermodynamics

The study of energy and its transformations.

work (w)

The energy transferred when an object is moved by a force.

acid

in common laboratory terms, any species that produces H+ ions when dissolved in water. (See also Arrhenius, Brønsted-Lowry, and Lewis acid-base.)

acid-base reaction

Any reaction between an acid and a base. (See also neutralization reaction.)

activity series of the metals

A listing of metals arranged in order of decreasing strength of the metal as a reducing agent in aqueous reactions.

aqueous solution

A solution in which water is the solvent.

base

In common laboratory terms, any species that produces OH− ions when dissolved in water. (See alsoArrhenius, Brønsted-Lowry,andLewis acid-base.)

concentration

A measure of the quantity of solute dissolved in a given quantity of solution (or of solvent).

dynamic equilibrium

The condition at which the forward and reverse reactions are taking place at the same rate, so there is no net change in the amounts of reactants or products.

electrolyte

A mixture of ions, in which the electrodes of an electrochemical cell are immersed, that conducts a current.

end point

The point in a titration at which the indicator changes color permanently.

equivalence point

The point in a titration when the number of moles of the added species is stoichiometrically equivalent to the original number of moles of the other species.

hydronium ion (H3O+)

A proton covalently bonded to a water molecule.

metathesis reaction

(alsodouble-displacement reaction) A reaction in which atoms or ions of two compounds exchange bonding partners. Precipitation and acid-base reactions are examples.

molarity (M)

A unit of concentration expressed as the moles of solute dissolved in 1 L of solution.

molecular equation

A chemical equation showing a reaction in solution in which reactants and products appear as intact, undissociated compounds.

net ionic equation

A chemical equation of a reaction in solution in which spectator ions have been eliminated to show the actual chemical change.

non electrolyte

substance whose aqueous solution does not conduct an electric current.

oxidation

The loss of electrons by a species, accompanied by an increase in oxidation number.

oxidation number (O.N.)

(alsooxidation state) A number equal to the magnitude of the charge an atom would have if its shared electrons were transferred to the atom that attracts them more strongly.

oxidation-reduction reaction

(alsoredox reaction) A process in which there is a net movement of electrons from one reactant (reducing agent) to another (oxidizing agent).

oxidizing agent

The substance that accepts electrons in a reaction and undergoes a decrease in oxidation number.

polar molecule

A molecule with an unequal distribution of charge as a result of its polar bonds and shape.

precipitate

The insoluble product of a precipitation reaction.

precipitation reaction

A reaction in which two soluble ionic compounds form an insoluble product, a precipitate.

reducing agent

The substance that donates electrons in a redox reaction and undergoes an increase in oxidation number.

reduction

The gain of electrons by a species, accompanied by a decrease in oxidation number.

salt

An ionic compound that results from an acid-base reaction after solvent is removed.

solute

The substance that dissolves in the solvent.

solution

A mixture that has no visible boundaries among its components.

solvated

Surrounded closely by solvent molecules

solvent

The substance in which one or more solutes dissolve.

spectator ion

An ion that is present as part of a reactant but is not involved in the chemical change.

titration

A method of determining the concentration of a solution by monitoring the amount of a solution of known concentration needed to react with it.

total ionic equation

An equation for an aqueous reaction that shows all the soluble ionic substances dissociated into ions.

absorption spectrum

The spectrum produced when atoms absorb specific wavelengths of incoming light and become excited from lower to higher energy levels.

amplitude

The height of the crest (or depth of the trough) of a wave; related to the intensity of the energy (brightness of the light).

angular momentum quantum number (l)

An integer from 0 ton− 1 that is related to the shape of an atomic orbital.

atomic orbital

(alsowave function) A mathematical expression that describes the motion of the electron's matter-wave in terms of time and position in the region of the nucleus. The term is used qualitatively to mean the region of space in which there is a high probability of finding the electron.

d orbital

An atomic orbital withl= 2.

de Broglie wavelength

The wavelength of a moving particle obtained from the de Broglie equation: λ =h/mu.

diffraction

The phenomenon in which a wave striking the edge of an object bends around it. A wave passing through a slit as wide as its wavelength forms a circular wave.

electromagnetic radiation

Oscillating, perpendicular electric and magnetic fields moving simultaneously through space as waves and manifested as visible light, x-rays, microwaves, radio waves, and so on.

electromagnetic spectrum

The continuum of radiant energy arranged in order of increasing wavelength.

electron cloud depiction

An imaginary representation of an electron's rapidly changing position around the nucleus over time.

electron density diagram

(alsoelectron probability density diagram) The pictorial representation for a given energy sublevel of the quantity ψ2 (the probability density of the electron lying within a particular tiny volume) as a function ofr(distance from the nucleus).

emission spectrum

The line spectrum produced when excited atoms return to lower energy levels and emit photons characteristic of the element.

excited state

Any electron configuration of an atom (or ion or molecule) other than the lowest energy (ground) state.

f orbital

An atomic orbital withl= 3.

frequency (ν)

The number of complete waves, or cycles, that pass a given point per second, expressed in units of 1/second, or s−1 [also calledhertz(Hz)]; related inversely to wavelength.