Thermodynamics

Question 1

Heat

Answer 1

Thermal kinetic energy from the random motion of particles

Question 2

Exothermic

Answer 2

Heat goes from the system to the surroundings; heat is “released” (-)

Question 3

Endothermic

Answer 3

Heat goes from surroundings to system; heat is “absorbed” (+)

Question 4

Spontaneity

Answer 4

Whether or not a process occurs under a given set of conditions without a driving force

Question 5

Entropy

Answer 5

Energy dispersion disorder (number of microstates).

Question 6

The second law of Thermodynamics

Answer 6

For a process to be spontaneous entropy in the universe must increase

Question 7

What is the entropy order for s, l, and g

Answer 7

(s)<(l)«<(g)

Question 8

What causes entropy to increase

Answer 8

• Increase in temperature, higher the molecular complexity
• Increase in molar mass, the more something can move around
• Increase in moles of gas, and the higher the number of particles
• Increase in randomness of molecules; such as formation of a gas

Question 9

Spontaneous

Answer 9

Occurs as written

Question 10

What are the rules to determine entropy in aqueous solutions

Answer 10

The smaller the charge of the solute, the more entropy increases

Question 11

Why do smaller charges cause entropy to increase

Answer 11

Higher charged ions cause more order in the solution so the entropy decreases

Question 12

Third Law of Thermodynamics

Answer 12

For a pure crystalline substance at absolute zero (0 K), entropy equals 0

Question 13

How do you get the Δ S surroundings/entropy for a phase change?

Answer 13

ΔS = - ΔH/temp

Question 14

Gibbs free energy

Answer 14

Energy available to do something or energy needed to do something (in kj/mol)

Question 15

What does it mean if G is (+/-)

Answer 15

-G: spontaneous
+G: nonspontaneous

Question 16

G formula

Answer 16

ΔGrxn = ΔHrxn - T * Srxn

Question 17

How do you determine ΔG if you are given observations?

Answer 17

(+)   -   (-)  = always (-)
(-)    -   (+) = always (+)
(+)   -   (+)  = depends; as T rises, G becomes negative
(-)    -   (-) = depends; as T rises, G becomes positive

Question 18

Gibbs free energy formula without standard G

Answer 18

ΔG = -RTln(K)

Question 19

How to get quotient K/Q?

Answer 19

[reactants]
(only gas or aqueous included)

Question 20

Equilibrium rules

Answer 20

Q = K: at equilibrium
Q > K: too many products; reaction must proceed in reverse
Q < K: too few products; reaction must go forward

Question 21

How do you get the entropy of the universe?

Answer 21

ΔS universe = ΔS system + ΔS surroundings

Question 22

How do you get the boiling/melting point?

Answer 22

T = ΔHrxn / ΔSrxn

Question 23

How can you get heat given ΔH rxn?

Answer 23

Heat = moles x ΔHrxn / mole

Question 24

How do you get ΔS sub?

Answer 24

ΔS sub = ΔH sub * moles of element

Question 25

What can be used to predict spontaneity by itself?

Answer 25

ΔS universe and ΔG universe because of the second law and spontaneous processes have positive Δ

Question 26

How do you solve percent yield problems?

Answer 26

1. Balance the chemical equation 2. Convert given amounts to moles 3. Determine which part will be used up first 4. Convert moles of product to grams for the theoretical yield 5. Solve for percent yield A/T x 100

Question 27

How do you get Δ H/S vap?

Answer 27

Δ H/S gas - Δ H/S liquid

Question 28

How do you get Δ H/S fus?

Answer 28

Δ H/S liquid - Δ H/S solid

Question 29

How do you get the boiling point and melting point?

Answer 29

Tbp = Δ Hvap/Δ S vap Temp = Δ Hfus/Δ Sfus