UNIT 2

Question 1

What are the three laws of thermodynamics?

Answer 1

1st law: Energy cannot be created or destroyed

2nd law: All spontaneous energy serves to increase the entropy of the universe

3rd law: As temperature increases, entropy increases and vise verse

Question 2

What is a spontaneous process?

Answer 2

A process which can occur without outside sources; it increases entropy within the system.

Question 3

What is entropy?

Answer 3

Entropy is the amount of randomness/disorder in a system.

Question 4

Rank the states of matter in increasing entropy.

Answer 4

Solid < Liquid < Gas

Question 5

How do increases to the following factors impact entropy?
A) Temperature
B) Volume
C) Pressure
D) Molecular Size

Answer 5

A) increase temp INCREASES entropy

B) increase volume INCREASES entropy

C) increase pressure DECREASES entropy

D) increase size INCREASES entropy

Question 6

What are endothermic and exothermic processes?

Answer 6

Endothermic: reactions that ABSORB heat (+)
i.e. sublimation, melting, boiling

Exothermic: reactions that RELEASE heat (-)
i.e. deposition, condensing, freezing

Question 7

A) What is Gibbs Free Energy?
B) What is the Equation?

Answer 7

A) combines enthalpy and entropy at a given temperature; can be used to determine whether a process is spontaneous or not.

B) ΔG = ΔH - TΔS
ΔG = gibbs free energy
ΔH = Enthalpy
ΔS = Entropy
T = Temp (K)

Question 8

When using the Gibbs Free Energy Equation, how do we know whether a process is spontaneous or not?

Answer 8

A) When ΔG is POSITIVE, the process is NON-SPONTANEOUS

B) When ΔG is NEGATIVE, the process is SPONTANEOUS

Question 9

What do Enthalpy (ΔH) and Entropy (ΔS) tell us about a reaction?

Answer 9

ENTHALPY (ΔH):
A) when ΔH is positive, the reaction is ENDOTHERMIC (+), and that the reaction does NOT favor spontaneity

B) when ΔH is negative, the reaction is EXOTHERMIC (-), and the reaction favors spontaneity

ENTROPY (ΔS):
A) When ΔS is positive, disorder INCREASES which favors spontaneity

B) When ΔS is negative, disorder DECREASES which favors spontaneity

Question 10

What are the four combinations of ΔH and ΔS and what do they tell us?

Answer 10

1) -ΔH and +ΔS: Spontaneous at ALL temperatures

2) +ΔH and -ΔS:
NEVER spontaneous

3) +ΔH and +ΔS: spontaneous only at HIGH TEMPERATURES

4) -ΔH and -ΔS:
spontaneous only at LOW TEMPERATURES