Module 3

Question 1

Definition of internal energy

Answer 1

The energy that’s intrinsic to a material

Question 2

State functions

Answer 2

Tells us the state of the system.

Does NOT depend (mathematically) on how we got from A to B, just uses the initial and final conditions.

Value is dependent only on the state the system is in, never on how that state was reached.

Question 3

Path functions

Answer 3

(Mathematically) depends on how we got from A to B. Measures what happens in between the initial and final conditions.

Value is dependent on how the state of the system was reached.

Question 4

First Law of Thermodynamics

Answer 4

The energy of the universe is constant.

The total change in energy of a system consists of the heat transferred to (delta H or q) and the work done (w) on a system.

Question 5

If something releases heat, it is…

Answer 5

Exothermic

Question 6

If something absorbs heat, it is…

Answer 6

Endothermic

Question 7

Definition of specific heat capacity

Answer 7

The quantity of heat required to increase the temperature of one gram of a substance by one degree C/K

Question 8

Is delta H (change in enthalpy) a state function or a path function?

Answer 8

State function. It uses only the initial and final conditions.

Question 9

What does calorimetry measure?

Answer 9

Heat flow

Question 10

Is enthalpy (H) a state function or a path function?

Answer 10

It’s a state function.

Note that enthalpy values can’t be measured directly. Only changes in enthalpy can be determined.

Question 11

If delta H is negative…

Answer 11

…the rxn is exothermic, indicates that heat has been lost from the system.

Question 12

If delta H is positive…

Answer 12

…the rxn is endothermic, indicates that heat has been gained in the system.

Question 13

What does delta H predict?

Answer 13

Whether reactions will be endothermic or exothermic.

Question 14

What does entropy predict?

Answer 14

Whether reactions will be spontaneous or not.`

Question 15

Second Law of Thermodynamics

Answer 15

The entropy of the universe is increasing to a maximum.

Question 16

What happens to entropy if the temperature of the system increases while volume remains constant?

Answer 16

Entropy increases, delta S is positive

Question 17

What happens to entropy if the volume of the system increases while temperature remains constant?

Answer 17

Entropy increases, delta S is positive

Question 18

What happens to entropy if both the temperature and the volume of a system increase?

Answer 18

Entropy increases, delta S is positive

Question 19

What three properties do liquids have?

Answer 19

Viscosity (resistance to flow)

Surface tension

Vapor pressure

Question 20

What would make a liquid more viscous?

Answer 20

Decreasing the temperature, decreasing the IMFs present

Question 21

What would increase a liquid’s surface tension?

Answer 21

Strengthening the IMFs

Question 22

What would increase a liquid’s vapor pressure?

Answer 22

Weakening the IMFs, increasing temperature

Question 23

When at low temperatures is a rxn spontaneous?

Answer 23

At low temps, delta G is roughly equal to delta H.

Rxn must be edxothermic (delta H is negative) for it to be spontaneous.

Question 24

When at high temperatures is a rxn spontaneous?

Answer 24

At high temps, delta G is roughly equal to -TdeltaS.

Rxn must increase in entropy (delta S is positive) for it to be spontaneous.

Question 25

How does delta G predict spontenaity?

Answer 25

When delta G is negative, rxn is spontaneous. When delta G is positive, rxn is NOT spontaneous, instead the reverse rxn is spontaneous. When delta G = 0, the system is at equilibrium and neither the forwards nor reverse rxns are spontaneous.

Question 26

Where does vapor pressure come from?

Answer 26

Particles at the surface of a liquid having enough kinetic energy so that they can escape the IMFs holding them in the liquid, vaporizing and entering the gas state above the liquid.

Question 27

What would decrease a liquid's boiling point?

Answer 27

Weakening the IMFs, lowering the external pressure

Question 28

Breaking bonds is...

Answer 28

...endothermic.

Question 29

Forming bonds is...

Answer 29

...exothermic.

Question 30

When will a liquid boil?

Answer 30

When it's vapor pressure is equal to the external pressure.

Question 31

Why would a rxn be endothermic?

Answer 31

More bonds are created than broken. More moles of stuff are created/present at the end of the rxn.

Question 32

What is Gibbs Free Energy (G)?

Answer 32

Combines enthalpy and energy. Whether G is positive or negative allows us to predict a rxn's spontenaity, and thus whether or not it will occur. It also tells us how much of a particular type of work a thing/system can do.

Question 33

How do we find at what temperature a rxn will become spontaneous, aka its crossover temp?

Answer 33

Set delta G = 0, then solve. When delta G = 0, the system is at equilibrium. It marks the crossover temp/point from spontaneous to non-spontaneous. deltaG = 0 = deltaH - TdeltaS

Question 34

Why is water a poor ideal gas?

Answer 34

Because it has a lot of IMFs holding it together, causing its collisions to be less than perfectly elastic.

Question 35

Why do gases turn into liquids (condense) when the ideal gas law states that they shouldn't?

Answer 35

IMFs

Question 36

Which state of matter has more entropy: solid, liquid, or gas?

Answer 36

Gas

Question 37

What are London Dispersion Forces and where do they come from?

Answer 37

LDFs are the weakest IMF. They exist in al matter and arise from the transient fluctuating dipole in each electron cloud inducing a similar dipole in neighboring electron clouds.

Question 38

What kinds of IMFs are found in pure noble gas samples?

Answer 38

Only London Dispersion Forces

Question 39

What would increase a molecule's LDF?

Answer 39

Increasing surface area and mass

Question 40

What are dipole-dipole interactions and where do they come from?

Answer 40

Occurs only in intrinsically polar molecules, molecules with a permanent dipole.

Question 41

What would increase dipole-dipole IMFs?

Answer 41

Having a larger individual/intrinsic dipole, caused by a larger electronegativity difference in the molecule

Question 42

What are hydrogen bonding IMFs and where do they come from?

Answer 42

Subset of dipole-dipole IMFs that arise because hydrogen is so small it can get really close to the next atom/molecule. Occurs only between hydrogen and either oxygen, nitrogen, or fluorine.

Question 43

What are ion dipole IMFs and where do they come from?

Answer 43

Occurs when a molecule with an intrinsic dipole interacts with a dissolved ion, causing the molecules to orient themselves in certain ways

Question 44

What would increase ion dipole IMFs?

Answer 44

Increasing the ionic charge of the dissolved ion

Question 45

The heat of condensation describes...

Answer 45

...condensing. Gas to liquid.

Question 46

The heat of vaporization describes...

Answer 46

...vaporizing. Liquid to gas.

Question 47

The heat of crystallization describes...

Answer 47

...freezing. Liquid to solid.

Question 48

The heat of fusion describes...

Answer 48

...melting. Solid to liquid.

Question 49

What properties are solids dependent on?

Answer 49

Type of particle, the geometry of the particles in arrangement, and the forces holding the particles together

Question 50

What are the four types of crystalline solids?

Answer 50

Ionic, metallic, covalent network, and molecular

Question 51

What type of crystalline solid conducts electricity as a liquid but not as a solid, has a very high melting point, and is very brittle?

Answer 51

Ionic solid

Question 52

What type of crystalline solid is good at conducting heat and electricity and is made out of electropositive elements?

Answer 52

Metallic solid

Question 53

What type of crystalline solid is not conductive, has a very high melting point, and is very hard?

Answer 53

Covalent network solid

Question 54

What type of crystalline solid is made of atoms from electronegative elements?

Answer 54

Covalent network solid

Question 55

What type of crystalline solid is malleable and ductile and has a variable hardness and melting temp?

Answer 55

Metallic solid

Question 56

What type of crystalline solid has a low melting point and is held together by IMFs?

Answer 56

Molecular solids

Question 57

What type of crystalline solid is made of nonmetal element compounds, in building blocks of molecules, and is held together by IMFs?

Answer 57

Molecular solids

Question 58

What is sublimation?

Answer 58

Phase change from solid to gas, without become a liquid in between

Question 59

What is a triple point?

Answer 59

The temperature and pressure at which the three phases of a substance coexist in thermodynamic equilibrium.

Question 60

What is a critical point?

Answer 60

The end point of a phase equilibrium curve, where phase boundaries vanish. In the case of the liquid-vapor critical point, its the temp and pressure above which a substance exists as a supercritical fluid

Question 61

Order the four IMFs from strongest to weakest.

Answer 61

Ion-dipole, hydrogen bonding, dipole-dipole, LDFs

Question 62

What is deposition?

Answer 62

Phase change from a gas to a solid, without becoming a liquid in between.

Question 63

In a unit cell, corner-centered atoms count as...

Answer 63

1/8

Question 64

In a unit cell, face centered atoms count as...

Answer 64

1/2

Question 65

In a unit cell, edge centered atoms count as...

Answer 65

1/4

Question 66

In a unit cell, body centered atoms count as...

Answer 66

1

Question 67

Which solid crystalline structure features separate bonding and inter-particle force interactions?

Answer 67

Molecular covalent solids