exam 4

Question 1

what is thermodynamics?

Answer 1

the study of energy and its transformation

Question 2

what is entropy

Answer 2

heat transferred between the system and its surroundings
(a measure of randomness or disorder of a system)

Question 3

1st law of thermodynamics

Answer 3

energy is neither created nor destroyed
Delta E= q+w
Delta E is change in internal energy
q is the heat absorbed by the system from the surrounding
w is work done

Question 4

what happens when q is greater than 0

Answer 4

the system absorbs heat from surroundings

Question 5

what happens when q is less than 0

Answer 5

system releases heat to the surroundings

Question 6

what happens when w is greater than 0

Answer 6

surroundings are doing work on the system

Question 7

what happens when w is less than 0

Answer 7

system is doing work on the surroundings

Question 8

what are spontaneous processes

Answer 8

proceeds on its own without assistance
ice melting on a hot day; when you drop an egg and it is cracked
a process that is spontaneous in one direction is nonspontaneous in the opposite direction

Question 9

what are non spontaneous processes

Answer 9

the reverse of a spontaneous processess
ex: breaking an egg and expecting it to go back together

Question 10

reverse process

Answer 10

the change occurs in a way that the system + surroundings can be restored to their original state by EXACTLY reversing the change (the change has to be very small)

Question 11

irreversible process

Answer 11

cannot simply be reversed to restore the system + surroundings to its original state, you have to change something in the system to restore it back to its original state

Question 12

what is the second law of thermodynamics

Answer 12

-entropy always increases; the reason why you cannot unscramble an egg; chaos moves towards more chaos
Delta S= qrev/T
qrev is the amount of heat added reversibly to the system
- any irreversible process results in an increase in total entropy whereas any reversible process results in no overall change in entropy

Question 13

isothermal process (constant T)
Delta S for phase changes

Answer 13

DeltaS fusion = qrev/T = DeltaH fusion / T

entropy change; constant temperature
Delta S = entropy ; qrev = heat transferred in a reversible process at constant T
Delta H units are kj/mol

Question 14

reversible process equation

Answer 14

Delta S univ= Delta S System + Delta S surroundings = 0

Question 15

irreversible process equation

Answer 15

Delta S univ= Delta S sys+ Delta S surr > 0

Question 16

how can you increase entropy

Answer 16

• increase number of moles
• increase volume
• increase with temp
• increase when gases form from liquid to solids
• liquid or solutions form solids
• number of gas molecules increase during a chemical rxn

Question 17

third law of thermodynamics

Answer 17

the entropy of a pure crystallite substance at absolute zero
K if we lower T, we slow down all processes
standard state = 298K

Question 18

S knot

Answer 18

standard molar entropy ; units J/mol-K

Question 19

gibbs free energy equation

Answer 19

spontaneous process that result in a positive in the systematic entropy are always exothermic

Delta G= Delta H^o - T(Delta S^o)
T is 298K ; Delta H change in enthalpy from reactants to products ; Delta S is change in entropy disorder

Question 20

gibbs free energy Delta G relations

Answer 20

Delta G < 0 rxn is spontaneous in a forward direction
Delta G > 0 rxn is non spontaneous in forward direction
Delta G = 0 rxn is at equilibrium

Question 21

free energy + temp

Answer 21

Delta G = Delta H + (-T Delta S)
Delta H is enthalpy
-T Delta S is entropy

Question 22

Delta H < O and Delta S > 0

Answer 22

spontaneous at all T
Delta G < 0

Question 23

Delta H > 0 and Delta S > 0

Answer 23

• spontaneous at increase T
• non spontaneous at decrease T

Question 24

Delta H < 0 and Delta S < 0

Answer 24

• spontaneous at decrease T
• non spontaneous at increase T

Question 25

Delta H > 0 and Delta S < 0

Answer 25

nonspontaneous at all T
Delta G > 0