Thermo 3 Energy Enthalpy Entropy

Question 1

What is the equation for Enthalpy

Answer 1

H= E+PV

E is energy

Question 2

What types of reactions does Enthalpy include

Answer 2

Adiabatic + isobaric reactions

Question 3

What is an isobaric reaction

Answer 3

Constant pressure environment

Question 4

Since we assume Enthalpy is at constant pressure (isobaric) and adiabatic what does the equation turn into

Answer 4

From H=E+PV to delta H= dQ + VdP

But since constant pressure

delta H= dQ p (p to show constant pressure)

Question 5

A change in Enthalpy generally means what

Answer 5

A change in heat (delta Q)

Question 6

Is Enthalpy temperature independent or dependent

Answer 6

Temp dependent

Question 7

What are the laws of thermodynamics

Answer 7

Temperature maps thermodynamic equilibrium: If T1=T2 and T2=T3, Then T1=T3

Energy is cosereved: delta U = W+Q

Entropy increases : delta S >/_ zero (

Question 8

What happens if entropy is zero

Explain the absolute zero saying

Answer 8

Nothing happens

By extension of the first law, to reach absolute zero you would need something colder than absolute zero to cool it to absolute zero (temp equilibrium)

Question 9

What is heat death

Answer 9

Entropy gradually increase

So eventually the universe gains so much disorder, leading to the death of the universe

Question 10

Whag is entropy

Answer 10

Disorder

The energy accessible to be used as work

Question 11

Entropy equation

Answer 11

S=KB ln (ohm)

Question 12

Explain the temperature increase effects on entropy from solid to liquid

Answer 12

First heating the solid to the melting temp increases the entropy because more vibrations of molecules in the ordered crystal array (can see some defects)

Melting the solid at Tm increase entropy by breaking up the ordered array

During this melting the T is constant but S is increasing because more defects in the crystal

During this melting the solid and liquid are in thermal equilibrium (no heat transfer between them since at same temp)

Question 13

Explain the temperature increase effects on entropy from liquid to gas

Answer 13

Heating the liquid increases S because more vibration and rotation of molecules, random movement as the molecules roll around each other

Then evaporating that liquid at Tbp increases S because of separation of the atoms in the liquid

The temp is constant during the evaporation

The liquid and gas are in thermal equilibrium during evaporation

Question 14

Explain the temperature increase effects on entropy when heating a gas

Answer 14

The S increasing when heating the gas because more rotation and new vibrations

Question 15

Explain the entropy vs temp plot

Answer 15

Entropy vs temp

At the Tb and the Tm there is a jump in entropy but the temp stays the same

Question 16

What is the equation for the energy accessible to be used as work

What is meant by reversible

Answer 16

Delta S = Q reversible / T

System is constantly in eqauillibrium with surrounding

No spontaneus direction of change at any point

If you have 2 things in equaillibrium, Infinitismal changes in system/surrounding with always reeqillibriate

Question 17

What are reversible adiabats

What are reversible isotherms

Answer 17

Reversible adiabats: the entropy of the system doesn’t change

Reversible isotherm: the entropy of the system and surrounding doesn’t change

Question 18

If the system is reversible and isothermal What is the equation for delta S

Answer 18

The change in energy is zero (delta U=0)

Delta S = nR ln (Vf/Vi)

Question 19

Explain how to find microstates

Answer 19

The number of microstates correspond to the number of positions a thing can occupy

If two macrostates find the number of microstates and multiply them together

If all in one box only one microstate

if half and half, two microstates since each particle can end up in two possible places

Question 20

Explain how to do statistical entropy to find entropy from microstates

Answer 20

Have one with 1 microstate and another with 2 microstates

Ohm is microstates

S = KB ln (ohm)

Delta S = kb ln (ohm2/ohm1)

If ohm is proportional to V^N

Delta S= NKb ln (V2/V1)

Question 21

Explain the entropy of mixing

Explain how entropy is additive

Answer 21

When two ideal gasses that were intially separated are mixed together the entity increases

The S total = S system + S surroundings

Question 22

What two equations do you get if you have constant pressure and constant volume with delta S

Answer 22

The helm holtz free energy (constant volume and temp)

The Gibbs free energy (constant pressure and temp)

Question 23

What are partition functions and ensembles

Answer 23

Characterize entropy as the probability of a particular microstate

Also finds the energies all the particles can occupy

Question 24

What does the microcanonical ensemble

Canonical

Grand canonical

Tell us

Answer 24

Mocrocanonical (energy can’t be exchanged out of a system)

Canocnal

Grand canonical (particles and energy are exchanged)