Chapter 3: Thermodynamics

Question 1

Temperature measures these parts of internal energy…

Answer 1

Rotational
Transitional
Vibrational

Question 2

6 Internal Energies

Answer 2

1. ) Vibrational Energy- atoms vibrations within a molecule; atoms in monatomic gas have NO vibrational energy
2. ) Rotational Energy- molecular movement where spatial orientation of the body changes and center of mass remains fixed; Atoms in a monatomic gas have NO rotational energy
3. ) Transitional energy- movement of center of mass of a molecule
4. ) Electronic Energy- potential electrical energy created by attractions b/n electrons and their nuclei; below 5000K, all molecules are at lowest energy level and if no molecular run occurs, electronic energy remains ms constant
5. ) Intermolecular potential energy- energy created by the intermolecular forces b/n molecular dipoles; gas at room temp & pressure, IPE makes small contribution to internal energy but at higher pressure contributions become more significant
6. ) Rest Mass energy- energy predicted by e=mc^2

Question 3

Seven state functions

Answer 3

Title. State function. Prefix
1 Internal Energy. U
2 Temperature. T
3 Pressure. P
4 Volume. V
5 Enthalpy. H
6 Entropy. S
7 Gibbs energy. G

Question 4

Zeroth law of thermodynamics states…

Answer 4

That temperature exists

Question 5

Internal energies (vibrational, transitional, and rotational) describe energies of ….

Sum of these energies is called

Relationship in Increase in thermal energy is

Answer 5

Molecular motion

Thermal energy

Increase in temperature

Question 6

Molecules vibrate faster in a…

Molecules in a solid only…

Answer 6

Solid as temps increase

Vibrate

Question 7

Define enthalpy

Answer 7

H=U+PV

Units for Enthalpy is joules (energy)

(U=internal energy)

Question 8

Change in enthalpy

Answer 8

(Delta)H=(delta)U+P(delta)V

Question 9

Catalysts do not affect…

Answer 9

Equilibrium and enthalpy change

Question 10

Catalyst affect …

Answer 10

The rate

Question 11

What’s Entropy

Answer 11

Natures tendency toward “disorder” or the concept of “probability”

Question 12

Second Law Thermodynamics

Answer 12

Entropy of isolated system will never decrease

Question 13

The sum of entropy is…

Answer 13

Change of entropy system + change in surroundings = change in universe > or = 0

Question 14

Entropy of system can ___________ only if at the same time the surroundings __________ by > or = magnitude

Answer 14

Decrease

Increases

Question 15

Entropy dictates what?

Answer 15

Direction of a reaction

Question 16

Entropy increases with…

Answer 16

Number
Volume
Temperature

If a reaction INCREASES the NUMBER of gaseous molecules, then the reaction has (+) entropy

Question 17

Units of entropy

Answer 17

J/K

Question 18

Change in entropy process will be the SAME as change in entropy for a _______ process between same 2 states

Answer 18

Reversible

Question 19

Entropy is an EXTENSIVELY property which means…

Answer 19

It INCREASES with amount of substance

Question 20

Three types of equilibrium

Answer 20

Mechanical - when system is NOT accelerating

Material - in material when no net chemical reaction is occurring and there’s no matter transferring within the system

Thermal - when temp is the SAME throughout; can also be in thermal equilibrium with its surroundings, meaning that’s the SAME temp as its surroundings

Question 21

Important MCAT Equation: Gibbs Free Energy (G)

Answer 21

(Delta)G=(delta)H-T(delta)S

Refer to system and NOT surrounding

Question 22

(Delta)G=0 which means…

-(delta)G indicates _______ reaction

Answer 22

Equilibrium

Spontaneous

Question 23

Examples of non-PV work

Answer 23

Contracting muscles
Transmitting nerves
Batteries

Question 24

Gibbs free energy represents the maximum ….

Answer 24

Non-PV work available from a reaction

Question 25

Gibbs function [(delta)G, (delta)S, (delta)H] refer to changes in the ….

Gibbs is a function of both…

Answer 25

System

Enthalpy and entropy

Question 26

Reaction produces ____ change in enthalpy and a _____ change in entropy, the reaction can NEVER be the spontaneous.

Reaction produces a ____ change in enthalpy and a _____ change in entropy, it must be SPONTANEOUS.

If signs of both enthalpy and entropy are the same for a reaction, then the spontaneity of the reaction will depend on _______.

Answer 26

Positive; Negative

Negative; Positive (decreasing; increasing)

Temperature

Question 27

Oth Law

1st Law

2nd Law

3rd Law

Answer 27

• Temp exists and is a state function (2 bodies with the same system are in equilibrium with the SAME system in thermal equilibrium
• Energy of an isolated system is conserved for any reaction
• Entropy of the universe INCREASES for any reaction
• Perfect crystal at 0 K is assigned an entropy value of 0. All other substances and temps have a (+) entropy value

Question 28

Summary:

1) heat and work are the only two ways to change the energy of a _________.
2) heat and work result in the change in ______ energy of a system at REST.
3) Temperature is as _______ and Pressure is as _______.
4) Think of enthalpy as ______, or think of change in enthalpy at CONSTANT pressure as ______.
5) Think of ENTROPY as the __________.
6) Entropy _________ with _______, _________, and __________.
7) Gibbs energy change is as a _____ of maximum amount of energy available to do _______ work such as electrical work in a cell.

Answer 28

1) SYSTEM
2) INTERNAL
3) thermal/mole and thermal/vol
4) U+PV; heat
5) SPREADING of energy
6) INCREASES with temperature, volume, and numbers
7) NEGATIVE; nonPV work