THERMODYNAMICS

Question 1

1st Law of Thermodynamics

Answer 1

Energy cannot be created or destroyed.

INTERNAL ENERGY of an ISOLATED system is CONSTANT.

ΔE = E(FINAL) – E(INITIAL)

Question 2

EXOTHERMIC

____ enthalpy

Answer 2

Heat transfer TO surroundings

-ΔH
Bonds formed are STRONGER than broken.

Question 3

ENDOTHERMIC

___ enthalpy

Answer 3

Reaction requires/absorbs heat

+ΔH
Bonds formed are WEAKER than broken.

Question 4

OPEN SYSTEM

Answer 4

Exchanges matter & energy with surroundings

Question 5

CLOSED system

Answer 5

Exchanges energy with the surroundings (not matter)

Question 6

ISOLATED system

Answer 6

neither energy nor matter exchanged with surroundings

Question 7

STATE functions

Answer 7

value depends only on present state of system, not path used to arrive

Question 8

EXPANSION WORK equation

Answer 8

w = F x d

Question 9

ENTHALPY (H)

ΔH =
ΔH =

Answer 9

Heat change during a reaction at constant pressure.

State function.

ΔH = H (products) – H (reactants)
ΔH = H (Bond BREAKING) - H (MAKING)
ΔH = ΔE + PΔV

Question 10

Enthalpy of FUSION

Answer 10

Heat required to melt a substance without changing its temp.

Question 11

Enthalpy of VAPORISATION

Answer 11

Heat required to vaporise a substance without changing temp.

Question 12

Enthalpy of SUBLIMATION

Answer 12

Heat required to convert a substance from solid to gas directly.

Question 13

CALORIMETRY

Answer 13

Measure HEAT FLOW at CONSTANT
(A) PRESSURE, ΔH.
(B) VOLUME, ΔE

Question 14

Heat capacity (C)

Answer 14

Heat required to raise the temp. of a substance by a specific amount.

q = C x ΔT

Question 15

Molar Heat Capacity (Cm)

Answer 15

Heat required to raise temp. of 1 mol of substance by 1 C.

q = Cm x mols x ΔT

Question 16

Specific Heat Capacity

Answer 16

Heat required to raise the temp. pf 1g substance by 1 C.

q = C m ΔT

Question 17

Hess’ Law

Answer 17

Overall ENTHALPY change is the sum of all the individual steps of the reaction.

ΔH = ΔH1 + ΔH2

Question 18

Standard Enthalpy of Formation ΔH

Answer 18

Heat change when 1 mol of compound forms from its elements under standard conditions.

Question 19

Standard enthalpy of formation of an element in its standard state =

Answer 19

0

= ΔH products - ΔH reactants

Question 20

Bond dissociation energy

Answer 20

energy required to break a chemical bond of a molecule in its gaseous state & energy released when the bond forms.

Question 21

Bond enthalpy values depend on

Answer 21

Bond order
Electronic environment of atoms comprising a bond.
IN GASEOUS PHASE

Question 22

Bond enthalpy =

Answer 22

Bond enthalpy = ΔH reactant - ΔH product bonds

Question 23

Standard enthalpy of Combustion

Answer 23

ΔH per mol of combustible substance.

Question 24

ΔH

Answer 24

Heat change in a reaction at constant pressure.

Question 25

ΔS

Answer 25

Amount of freedom of motion / randomness in a system. State function

Question 26

SPONTANEOUS reaction: | _ΔH, _ΔS

Answer 26

-ΔH, +ΔS

Question 27

NON-SPONTANEOUS reaction: | _ΔH, _ΔS

Answer 27

+ΔH, -ΔS

Question 28

ΔS =

Answer 28

ΔS = S(FINAL) - S(INITIAL) ΔS=q(rev)/T = heat reversibly transfered to substance / temp. (ENTROPY OF HEATING WATER)

Question 29

2nd law of thermodynamics

Answer 29

entropy of the universe INCREASES in a spontaneous process.

Question 30

3rd law of thermodynamics

Answer 30

entropy of a perfectly ordered crystalline substance at 0K is ZERO. ATOMS ARE STATIONARY at absolute zero -> ZERO ENTROPY.

Question 31

ENTROPY is greatest in gases and less in solids. | T or F

Answer 31

T

Question 32

SPONTANEOUS PROCESS: ΔS(universe) = | EQUILIBRIUM: ΔS(universe) =

Answer 32

``` ΔS(universe) = ΔS(sys) + ΔS(sur) > 0 ΔS(universe) = ΔS(sys) + ΔS(sur) = 0 ```

Question 33

Standard molar entropy

Answer 33

entropy of 1 mol of pure substance at 1 atm & specified temp.

Question 34

Bond DISSOCIATION (breaking) is a ___thermic process

Answer 34

ENDO

Question 35

Bond ASSOCIATION (making) is a ___thermic process

Answer 35

EXO

Question 36

State the equation for bond enthalpies relating bond dissociation & association

Answer 36

ΔH = H (BOND BREAKING) – H (BOND MAKING)

Question 37

SPONTANEOUS process | _ΔH, _ΔS

Answer 37

-ΔH, +ΔS

Question 38

NON-SPONTANEOUS | _ΔH, _ΔS

Answer 38

+ΔH, -ΔS

Question 39

ENTROPY, S

Answer 39

Measure of freedom of motion / randomness / DISORDER in a system

Question 40

Compare the entropy of solid, liquid, and gaseous states

Answer 40

S(SOLID)

Question 41

Relate entropy and heat reversibly transferred to a substance.

Answer 41

ΔS = q REV / T

Question 42

SPONTANEOUS processes: | ΔS(UNIV) = ΔS(SYS) __ ΔS(SUR) __ 0

Answer 42

ΔS(UNIV) = ΔS(SYS) + ΔS(SUR) > 0

Question 43

EQUILIBRIUM processes: | ΔS(UNIV) = ΔS(SYS) __ ΔS(SUR) __ 0

Answer 43

ΔS(UNIV) = ΔS(SYS) + ΔS(SUR) = 0

Question 44

Standard molar entropy

Answer 44

entropy of 1 mol of pure substance at 1 atm pressure and a specified temp.

Question 45

Standard entropy of reaction

Answer 45

entropy change for a reaction at 1 atm and 25 C.

Question 46

RELATE G, H, T and S.

Answer 46

ΔG = ΔH – TΔS

Question 47

SPONTANEOUS _ΔS _ΔG

Answer 47

+ΔS | -ΔG

Question 48

NON-SPONTANEOUS: _ΔS _ΔG

Answer 48

- ΔS | + ΔG

Question 49

EQUILIBRIUM _ΔS _ΔG

Answer 49

``` ΔS = 0 ΔG = 0 ```

Question 50

What does IC50 measure

Answer 50

INHIBITOR POTENCY: inhibitor conc which reduces enzymatic activity by 50%.

Question 51

EXERGONIC | _ΔG

Answer 51

Reaction releases more energy than it consumes. | -ΔG

Question 52

ENDERGONIC | _ΔG

Answer 52

Reaction consumes more energy than it releases. | +ΔG