Ch. 7: Thermochemistry

Question 1

Can an Isolated System exchange energy or matter with the surroundings

Answer 1

no exchange of energy (heat or work) with surroundings

ex: insulated bomb calorimeter

Question 2

Can a Closed System exchange energy or matter with the surroundings

Answer 2

exchange of energy (heat or work) but not matter with surroundings

ex: steam radiator

Question 3

Can an Open System exchange energy or matter with the surroundings

Answer 3

exchange of energy (heat or work) and matter with surroundings

ex: pot of boiling water

Question 4

what is a process

Answer 4

changing in one of the properties of a system

Question 5

equation for delta U

Answer 5

delta U = Q - W

change in internal energy of a system = heat added - work done by system

FIRST LAW OF THERMO

Question 6

what occurs in an isothermal process

Answer 6

• temperature is constant
• U (total internal energy) is constant, delta U = 0
• Q = W

Question 7

what occurs in an adiabatic process

Answer 7

• no heat is exchanged between system and environment (temperature can change)
• Q = 0
• delta U = - W (change in internal energy = work done on the system)

Question 8

what occurs in an isobaric process

Answer 8

• pressure is constant

- delta U = Q - W

Question 9

what occurs in an isovolumetric (isochoric) process

Answer 9

• volume is constant
• no change in volume = W = 0
• delta U = Q

Question 10

how is a spontaneous process driven

Answer 10

occurs internally WITHOUT drive by outside energy source

Question 11

what is accomplished by coupling

Answer 11

energy for nonspontaneous rxns is supplied by linking them with spontaneous rxns

Question 12

state functions

Answer 12

properties of a system at equilibrium

• pressure (P)
• density (p)
• temperature (T)
• volume (V)
• enthalpy (H)
• internal energy (U)
• Gibbs free energy (G)
• entropy (S)

Question 13

process functions

Answer 13

properties of a system in flux

• work (W)
• heat (Q)

Question 14

standard condition

Answer 14

• 25 degrees C (298K)
• 1 atm
• 1 M con’c

used for kinetics, e’q, and thermo, measuring H, G, S

Question 15

standard temperature and pressure

Answer 15

• 0 degrees C (273K)
• 1 atm

used for ideal gas calculations

Question 16

what is the standard state of a substance

Answer 16

the most stable state of the substance under standard conditions

Question 17

evaporation/vaporization

Answer 17

liquid to gas phase change

molecules near the surface of liquid have enough kinetic energy to escape into the gas phase

Question 18

condensation

Answer 18

gas to liquid phase change

molecules are forced by a lower temperature or higher pressure back into the liquid phase

Question 19

fusion/melting

Answer 19

solid to liquid phase change

molecules in the solid absorb enough energy to break into liquid phase

Question 20

solidification/crystallization/freezing

Answer 20

liquid to solid phase change

Question 21

sublimation

Answer 21

solid to gas phase change

Question 22

deposition

Answer 22

gas to solid phase change

Question 23

triple point

Answer 23

point at which three boundaries meet on a phase diagram

Question 24

critical point

Answer 24

point at which the phase boundary for liquid and gas terminate
(no distinction between the phases at this point)

Question 25

what does temperature measure

Answer 25

average kinetic energy of particles of a substance

Question 26

what does heat measure

Answer 26

transfer of energy from one substance to another as a result of difference in temperature

Question 27

endothermic process delta Q

Answer 27

delta Q > 0 system absorbs heat

Question 28

exothermic process delta Q

Answer 28

delta Q < 0 system releases heat

Question 29

calorimetry

Answer 29

the process of measuring transferred heat

Question 30

equation for heat absorbed/released in a process

Answer 30

q = m*c*delta T heat = mass * specific heat * change in temperature

Question 31

specific heat (c)

Answer 31

amount of energy required to raise the temperature of one gram of substance by one degree C or K

Question 32

equation for heat capacity

Answer 32

m*c

Question 33

equation for heat absorbed/released during a phase change

Answer 33

q = m*L heat = mass * latent heat

Question 34

latent heat

Answer 34

enthalpy of an isothermal process

Question 35

what does changes in enthalpy represent for a reaction

Answer 35

changes in heat at constant pressure

Question 36

equation for delta H of a reaction

Answer 36

delta H rxn = H products - H reactants

Question 37

endothermic process delta H

Answer 37

positive products have more heat than reactants heat is absorbed in reaction

Question 38

exothermic process delta H

Answer 38

negative products have less heat than reactants heat is expressed in reaction

Question 39

standard element of formation

Answer 39

enthalpy required to produce one mole of a compound from its elements in their standard states

Question 40

standard enthalpy of a reaction

Answer 40

enthalpy change accompanying a rxn being carried out under standard conditions. delta H rxn at standard conditions

Question 41

Hess's Law

Answer 41

state function changes of a reaction are additive ENTHALPY, ENERGY, GIBBS FREE ENERGY

Question 42

bond dissociation energy

Answer 42

average energy that is required to break a particular bond type

Question 43

standard heat of combustion

Answer 43

enthalpy change associated with the combustion of a fuel

Question 44

what does changes in entropy measure

Answer 44

spontaneous dispersal of energy at specific temperature

Question 45

equation for entropy

Answer 45

delta S = Qrev / T change in entropy = heat gained/lost in reversible process / T in kelvin

Question 46

units of entropy

Answer 46

J / mol * K

Question 47

units of enthalpy

Answer 47

J * mol

Question 48

what does Gibbs free energy measure

Answer 48

maximum amount of energy released by a process occurring at a constant temp and pressure that is available to perform work

Question 49

equation for Gibbs free energy

Answer 49

delta G = delta H - [T*delta S] free energy = enthalpy - temp * entropy goldfish are horrible without tartar sauce

Question 50

exergonic reactions

Answer 50

- move toward eq' position - decrease in free energy - releases energy - spontaneous

Question 51

endergonic reactions

Answer 51

- move away from eq' position - increase in free energy - absorb energy - non spontaneous

Question 52

negative delta G

Answer 52

spontaneous

Question 53

positive delta G

Answer 53

nonspontaneous

Question 54

zero delta G

Answer 54

equilibrium delta H = T*delta S

Question 55

when is delta G temperature dependent

Answer 55

when delta S and delta H have the same sign