Chapter 17

Question 1

spontaneous process

Answer 1

• a process that occurs without outside intervention
• self-sustaining
• spontaneous DOES NOT = quick
• mostly exothermic, but not always
  
  • spontaneous endothermic rxns:
    
    • ice melting
    • water boiling
      
      • can both be spontaneous depending on temp and pressure
    • baking soda+room temp vinegar
    • making instant ice packs cold

Question 2

nonspontaneous process

Answer 2

a process that occurs only as long as energy is continually added to the system

Question 3

entropy(S)

Answer 3

• a measure of the dispersion of energy in a system at a specific temperature
• s state function(we only care about initial and final)
• ΔSsys=Sfinal - Sinitial

Question 4

second law of thermodynamics

Answer 4

• the total entropy of the universe increases in any spontaneous process
• universe=system+surroundings
• ΔSuniv = ΔSsys + ΔSsurr
• Spontaneous process in isolated system
  
  • ΔSsys>0
  • ΔSsurr = 0……so ΔSuniv>0
• SO a spontaneous process produces an increase in the entropy of the universe
• spontaneous: ΔSuniv>0
• nonspontaneous: ΔS<0

Question 5

reversible process

Answer 5

• a process that can be run in the reverse direction in such a way that, once the system has been restored to its original state, no net energy has flowed either to the system or to its surroundings
• happen so slowly that equilibrium is constantly maintained
  
  • not rly possible, but some rxns approximate reversibility
• energy flows spontaneously from a warm object to an adjacent cooler object
  
  • entropy+second law explain this mathematically

Question 6

third law of thermodynamics

Answer 6

• the entropy of a perfect crystal is zero at absolute zero
  
  • If we lower temp, lower particle KE, lower motion, lower entropy…..so if we lower temp to zero all motion should cease

Question 7

standard molar entropy(S°)

Answer 7

• the absolute entropy of 1 mole of a substance in its standard state and 298K, 1 atm
• Absolute entropies are determined from careful determinations of the molar heat capacity (or specific heat) of substances as a function of temperature
  
  • Ssolid < Sliquid < Sgas
• S° inc as # atoms per molec inc
  
  • b/c more bonds within a molecule=more opportunities for internal (vibrational) motion, and the greater the standard molar entropy

Question 8

3 factors that affect antropy change

Answer 8

1. Entropy increases when temperature increases
2. Entropy increases when volume increases
3. Entropy increases when the number of independent particles increase
   
   1. in all 3, entropy increases because each change increases the dispersion of the kinetic energy of a system’s particle

Question 9

Gibbs free energy(G)

Answer 9

• the maximum energy released by a process occurring at constant temperature and pressure that is available to do useful work
• If ΔGsys < 0, then ΔSuniv > 0, and the reaction is spontaneous
• If ΔGsys > 0, then ΔSuniv < 0, and the reaction is nonspontaneous. Instead, the reaction running in reverse is spontaneous
• If ΔGsys = 0, then ΔSuniv = 0, and the composition of the reaction mixture does not change. In other words, the reaction has reached chemical equilibrium.

Question 10

standard free energy of formation(ΔG_f^o)

Answer 10

• the change in free energy associated with the formation of 1 mole of a compound in its standard state from its component elements

Question 11

relationship btwn Q, K, and G

Answer 11

• When Q = K, ΔGrxn = 0 and the reaction is at equilibrium.
• When Q < K, ΔGrxn < 0 and the reaction is spontaneous.
• When Q > K, ΔGrxn > 0 and the reaction is nonspontaneous.

Question 12

influence of temp on equilibrium constants

Answer 12

• when ΔH^o < 0 or ΔS^o > 0, K is very large
  
  • aka rxn is spontaneous

Question 13

coupled rxns in living systems

Answer 13

add stuff from lecture

Question 14

microstate

Answer 14

• a unique distribution of particles among energy levels
• Each microstate represents one discrete way for the system to disperse all the energy in the system
• more microstates = more entropy

Question 15

3 types of motion O2 undergoes

Answer 15

1. translational motion as it zips around the space it occupies
2. rotational motion as it spins about imaginary axes perpendicular to the O=O bond
3. vibrational motion as its bonded atoms move toward and away from each other, like balls on the ends of a spring
   
   1. All 3modes of motion have one thing in common: the greater the thermal energy of the molecule, the greater each type of motion