Chapter 19 - Chemical Thermodynamics

Question 1

What is “chemical thermodynamics”? (Brief categorization)

Answer 1

The area of chemistry that deals with energy relationships.

Question 2

What is the first law of thermodynamics?

Answer 2

Energy is conserved (neither created nor destroyed).

Question 3

How is enthalpy mathematically expressed?

Answer 3

ΔE = q + w

ΔE is the change in the internal energy of a system

q is the heat absorbed or released by the system

w is the work done by or on the system

Question 4

What does q > 0 mean?

What does w > 0 mean?

Answer 4

It means that the system is gaining heat from the surroundings.

It means that the system is gaining work from the surroundings.

Question 5

What is a spontaneous process?

Answer 5

One that proceeds on its own without any outside assistance. It only goes in one direction.

Question 6

What is a nonspontaneous process?

Answer 6

The reverse of a spontaneous process. It does not occur without outside assistance (or at all, really).

Question 7

Thermodynamics tells us about the ____ and ____ of a reaction but not ____. What deals with the latter?

Answer 7

Thermodynamics tells us about the direction and extent of a reaction but nothing about the rate. Kinetics does that.

Question 8

What is a state function?

Answer 8

Properties that define a state and do not depend upon how we reach that state. Examples: temperature, internal energy, and enthalpy.

Question 9

What is a reversible process?

Answer 9

A specific way in which a system changes its state. We can restore the system back to its original state without a net change.

Question 10

What is an irreversible process?

Answer 10

One that cannot be reversed to restore the system to its original state without a net change.

Question 11

What is entropy?

Answer 11

The “randomness” of a system

Question 12

What is the second law of thermodynamics?

Answer 12

The entropy (“randomness”) of the universe is always increasing.

Question 13

What is a microstate?

Answer 13

A single possible arrangement of the positions and kinetic energies of the molecules when the molecules are in a specific thermodynamic state.

Question 14

What is Boltzmann’s entropy formula?

Answer 14

S = k • ln(W)

k is the Boltzmann constant: 1.38 • 10^-23 J/K

Question 15

Regarding the Boltzmann formula, entropy is a measure of what?

Answer 15

Entropy is a measure of how many microstates are associated with a particular macroscopic state.

Question 16

What is translational motion?

Answer 16

The movement from point A to point B, like throwing a baseball.

Question 17

What is rotational motion?

Answer 17

Motion of molecules in which they spin around an axis.

Question 18

What is vibrational motion?

Answer 18

Motion in which atoms periodically move towards and away from one another.

Question 19

The number of microstates possible for a system increase when ____ and why?

Answer 19

The number of possible microstates increases with an increase in temperature, volume, or number of molecules because these changes increase the possible positions and kinetic energies of the molecules making up the system.

Question 20

What is the third law of thermodynamics?

Answer 20

The entropy of a pure, perfect crystalline substance at absolute zero is zero: S(0K) = 0.

Question 21

What is the formula for Gibbs free energy?

Answer 21

ΔGº = ΔH - TΔS

H is enthaply

T is temperature

S in entropy

Question 22

Describe ΔG > 0, ΔG = 0, ΔG <0.

Answer 22

ΔG < 0 means the reaction is spontaneous in the forward direction.

ΔG = 0 means the reaction is at equilibrium

ΔG > 0 means the forward direction is nonspontaneous (work must be done to make it occur)

Question 23

In any spontaneous process carried out at constant temperature and pressure, what happens?

Answer 23

The free energy always decreases.