Chem 14B - Thermodynamics

Question 1

If no other energy is transferring:

Answer 1

∆U = w

Question 2

Formula for Volume change, no heat change:

Answer 2

w = P∆V or w = -P∆V (expansion, work)

Question 3

If energy is transferred ONLY as heat:

Answer 3

∆U = q

Question 4

Exothermic

Answer 4

Releases heat to surroundings, ∆H < 0

Question 5

Endothermic

Answer 5

Absorbs heat from surroundings, ∆H > 0

Question 6

If heat capacity is known:

Answer 6

q = C∆T; C = heat capacity

Question 7

∆U = q + w

Answer 7

U = internal energy. This formula is always true.

Question 8

At constant volume, heat transfer is interpreted as:

Answer 8

∆U;
q = ∆U;
U = total energy in a system

Question 9

At constant pressure, heat transfer is interpreted as:

Answer 9

∆H;
q = ∆H;
H = tracks losses & gains of energy as expansion or compression work during heat at constant pressure

Question 10

H = U + PV -> PV = nRT

Answer 10

∆H = ∆U + ∆n(gas)RT

Question 11

Isothermal:

Answer 11

No change in temperature. ∆T = 0
∆U = 0
∆U = 0 = q + w; q = -w or -q = w

Question 12

“Compresses reversibly”

Answer 12

Constant Pressure

Question 13

“in a bomb calorimeter”

Answer 13

Constant Volume

Question 14

Bomb Calorimeter Equation

Answer 14

q(cal) = C(cal)∆T

Question 15

Equation for reversible, isothermal expansion/compression:

Answer 15

w = -nRT ln (v2/v1)

Question 16

Equation for when system expands/compresses with constant external pressure:

Answer 16

w = -P∆V

Question 17

Equation if you know mass, specific heat and temperature change:

Answer 17

q = mC(s)∆T

Question 18

Equation if you know moles, specific heat, and temperature change:

Answer 18

q = nC(m)∆T

Question 19

Equation for melting (fusion) point phase change:

Answer 19

q(fus) = n∆H(fus)

Question 20

Equation for freezing point phase change:

Answer 20

q(freez) = -n∆H(fus) -> opposite of fusion

Question 21

Equation for vaporization phase change:

Answer 21

q(vap) = n∆H(vap)

Question 22

Equation for condensation phase change:

Answer 22

q(cond) = -n∆H(vap) -> opposite of vaporization

Question 23

Molar Heat Capacity: Constant Volume C(v,m), Atom

Answer 23

3/2R

Question 24

Molar Heat Capacity: Constant Volume C(v,m), Linear Molecules

Answer 24

5/2R

Question 25

Molar Heat Capacity: Constant Volume C(v,m), Nonlinear Molecules

Answer 25

3R

Question 26

Molar Heat Capacity: Constant Pressure C(p,m), Atom

Answer 26

5/2R

Question 27

Molar Heat Capacity: Constant Pressure C(p,m), Linear Molecule

Answer 27

7/2R

Question 28

Molar Heat Capacity: Constant Pressure C(p,m), Nonlinear Molecule

Answer 28

4R

Question 29

Entropy; S

Answer 29

State function;

Measure of disorder - Positional or Thermal

Question 30

Positional Disorder (entropy)

Answer 30

Disorder related to location of molecules; “will occupy empty space”

Question 31

Thermal Disorder (entropy)

Answer 31

Disorder due to thermal motion of molecules

Question 32

First Law of Thermodynamics

Answer 32

Change in internal energy of isolated system is zero

Question 33

Second Law of Thermodynamics

Answer 33

Entropy of isolated system increases during spontaneous process

Question 34

Equation for entropy change due to heating:

Answer 34

∆S = C ln (Tf/Ti)

Question 35

Equation for entropy change due to isothermal expansion:

Answer 35

∆S = nR ln (Vf/Vi)

Question 36

Equation for entropy change accompanying phase change (for 1 mole of substance):

Answer 36

∆S(vap) = q(vap)/T = ∆H(vap)/T

Question 37

What type of disorder (entropy) occurs at absolute zero?

Answer 37

Positional disorder (residual disorder)

Question 38

Third Law of Thermodynamics

Answer 38

Entropies of all perfect crystals approach zero as absolute temperature approaches zero.

Question 39

Equation for Residual Entropy if given molecules:

Answer 39

S = k(b) ln W^n;

k(b) is Boltzmann’s Constant (1.381 x 10^-23 J per K^-1

Question 40

Equation for Residual Entropy if given moles:

Answer 40

S = nR ln W

Question 41

List from least to greatest entropy: Gas, Liquid, Solid

Answer 41

Solid, Liquid, Gas

Question 42

Equation for Standard Reaction Entropy:

Answer 42

∆Sº = 𝚺nSº(m)(P) - 𝚺nSº(m)(R)

Question 43

Is reaction entropy positive or negative when gas is consumed?

Answer 43

Negative

Question 44

Is reaction entropy positive or negative when gas is created?

Answer 44

Positive