Thermochemistry

Question 1

process occurs at constant temperature

Answer 1

isothermal

Question 2

process exchanges no heat with environment

Answer 2

adiabatic

Question 3

process occurs at constant pressure

Answer 3

isobaric

Question 4

process occurs at constant volume

Answer 4

isochoric (isovolumetric)

Question 5

describe the physical properties of an equilibrium state; they are pathway independent; include: pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, and entropy

Answer 5

state functions

Question 6

T = 298 K, P = 1 atm, 1M concentrations

Answer 6

standard conditions

Question 7

T = 273 K, P = 1 atm; used for gas law calculations

Answer 7

standard temperature and pressure

Question 8

most prevalent form of an element under standard conditions

Answer 8

standard state

Question 9

exist at characteristic temperatures and pressures; include: fusion (melting), freezing (crystallization or solidification), vaporization (evaporation or boiling), condensation, sublimation, and deposition

Answer 9

phase changes

Question 10

at temperatures above this point, liquid and gas phases are indistinguishable

Answer 10

critical point

Question 11

temperature and pressure when all three phases of matter exist in equilibrium

Answer 11

triple point

Question 12

graphs the phases and phase equilibria for a system as a function of temperature and pressure

Answer 12

phase diagram

Question 13

a scaled measure of the average kinetic energy of a substance

Answer 13

temperature

Question 14

the transfer of energy that results from differences of temperature between two substances

Answer 14

heat

Question 15

a measure of the potential energy of a system found in intermolecular attractions and chemical bonds

Answer 15

enthalpy

Question 16

heat (q)

Answer 16

q = mc∆T

where:
c = specific heat

q = mL

where:
L = latent heat

Question 17

a measure of the degree to which energy has been spread throughout a system or between a system and its surroundings; maximized at equilibrium; unit = J/mol*K

Answer 17

entropy

Question 18

entropy (S)

Answer 18

S = Q(rev) / T

where:
Q(rev) = heat gained or lost in a reversible process

Question 19

derived from both enthalpy and entropy values for given system; also depends on temperature

Answer 19

Gibbs free energy

Question 20

change in Gibbs free energy (∆G)

Answer 20

∆G = ∆H - T∆S

Question 21

determines whether a process is spontaneous or nonspontaneous

Answer 21

change in Gibbs free energy (∆G)

Question 22

reaction proceeds in forward direction (spontaneous)

Answer 22

∆G < 0

Question 23

reaction is in dynamic equilibrium when ∆G = __

Answer 23

∆G = 0

Question 24

reaction proceeds in reverse direction (nonspontaneous)

Answer 24

∆G > 0

Question 25

∆G°(rxn)

Answer 25

∆G°(rxn) = -RT ln K(eq)