Lesson 9 - Thermodynamics

Question 1

Thermodynamics

Answer 1

The study of how work and heat relate to each other in chemical reactions and in changes of states

Question 2

Spontaneous Reaction

Answer 2

Reaction that occurs naturally under certain conditions.

-No continuous energy needed from external source.

Question 3

State Function

Answer 3

Value that depends on the state of the function and not the pathway that it took to get there.

Question 4

Extensive Property

Answer 4

Depends on the amount of matter in the sample.

Question 5

First Law of Thermodynamics
(Law of Conservation of Energy)

Answer 5

Energy can’t be created or destroyed only transferred.

Question 6

Second Law of Thermodynamics

Answer 6

For a spontaneous process, the entropy of the universe increases.

Question 7

Third Law of Thermodynamics

Answer 7

A perfect crystal at zero Kelvin has zero entropy.

Question 8

Entropy

Answer 8

How energy is distributed in the various motions of the molecules of the system.

Deals with randomness and disorder.

Question 9

Entropy Equation

Answer 9

S = k*ln(wf/wi)

Question 10

Microstates

Answer 10

Number of unique states that a system can exist in.

(The arrangement of atoms or molecules in a single instant).

Question 11

Boltzmann Constant (k or kb)

Answer 11

Relates the average kinetic energy of the gas molecules and temperature of the gas.

Question 12

Entropy Unit

Answer 12

J/K (joules/Kelvin)

Question 13

Boltzmann Constant (k or kb) - value w/ unit

Answer 13

1.38*10^-23 J/K

Question 14

Four Factors Affecting Entropy

Answer 14

1. Phase (s < l < g)
2. Temperature (higher temp = higher entropy)
3. Volume (higher volume = higher entropy)
4. # of particles/moles (more moles = higher entropy).

Question 15

Positive or Negative Delta S (Increase in gaseous moles from reactants to products)

Answer 15

Positive (order to disorder)

Question 16

Positive or Negative Delta S (s –> l –> g)

Answer 16

Positive (order to disorder)

Question 17

Three ways to predict if delta S is positive or negative.

Answer 17

1. Moles of gas (r –> products)
2. Phase changes (r –> products)
3. Complexity (only if there’s no changes in 1 or 2).

Question 18

Spontaneous or not (S < 0)

Answer 18

Nonspontaneous or spontaneous in opposite direction.

Question 19

Spontaneous or not (S > 0)

Answer 19

Very spontaneous.

Question 20

Spontaneous or not (S = 0)

Answer 20

At equilibrium.

Question 21

Entropy of Universe Equation

Answer 21

Delta S univ = Delta S (system) + (q surroundings/T)

q = heat
T = temperature (kelvin)
S = entropy
Delta = change

Question 22

Standard enthalpies (for how many moles under what conditions definition)

Answer 22

One mole of a substance under standard conditions.

Question 23

Three types of motions related to Entropy

Answer 23

1. Translational - describes how it moves.
2. Rotational - describes how molecules are to spin or rotate.
3. Vibrational - Describes the “toward and away” motion that atoms have w/ in molecules. (plucking a guitar).

Question 24

Relate freedom of molecule with the three types of motions and enthalpy

Answer 24

The freedom of a molecule increases with degrees of motion (translational, rotational, and vibrational).

Question 25

Relate temp with three types of motion and entropy

Answer 25

The higher the temp of a system the more motions (vibrational, translational, and rotational) and thus more entropy. The lower the temp, the less motions and less entropy.

Question 26

Gases have how many motions?

Answer 26

Three (translational, rotational, vibrational).

Question 27

What is the difference between ΔS and ΔS° for a chemical change?

Answer 27

ΔS is the actual change in entropy of the system while ΔS° is for under standard conditions.