Chapter 7: Thermochemistry

Question 1

What is the first law of thermodynamics?

Answer 1

∆U = Q - W

U = change in internal energy
Q = heat added
W = work done

Question 2

____________ processes occur when the system’s temperature is constant.

Answer 2

isothermal

Question 3

When U is constant, change in U is 0 and the first law simplifies to what?

Answer 3

Q = W
heat added equals work done by system

Question 4

____________ processes occur when no heat is exchanged between the system and the environment. The thermal energy of the system is constant.

Answer 4

adiabatic

Question 5

In adiabatic processes, Q = 0 and the first law simplifies to what?

Answer 5

∆U = -W
change in internal energy of system = work done on the system

Question 6

____________ processes occur when the pressure of the system is constant. Does not alter first law.

Answer 6

isobaric

Question 7

________________ processes experience no change in volume. No work is performed, so first law is:

Answer 7

isovolumetric; ∆U = Q

Question 8

What is a common method for supplying energy for nonspontaneous reactions?

Answer 8

Coupling nonspontaneous reactions to spontaneous ones

Question 9

What are the state functions?

When I’m under pressure and feeling dense, all I want to do is w

When I’m under pressure and feeling dense, all I want to do is watch TVand get HUGS

Answer 9

Pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, entropy

Question 10

State functions describe what?

Answer 10

The system in equilibrium state

Question 11

Standard conditions have been defined for measuring enthalpy, entropy, and Gibbs free energy. What are they?

Answer 11

25°C
1 atm pressure
1 M concentrations

used for kinetics, eq, and thermodynamics

Question 12

Liquid to gase phase is known as ________________

Answer 12

evaporation, or vaporization

Question 13

When liquid loses a high-energy particle, the temperature of the remaining liquid ____________.

Answer 13

decreases

Question 14

Boiling can only occur ________ the boiling point of a liquid and involves vaporization through the entire volume of the liquid.

Answer 14

above

Question 15

Gas back to liquid is ____________

Answer 15

condensation

Question 16

The temperature at which the vapor pressure of the liquid equals the ambient pressure is called the ____________ point.

Answer 16

boiling

Question 17

Transition from solid to liquid is ________

Answer 17

fusion, or melting

Question 18

Liquid to slid is ____________

Answer 18

solidification, crystallization, or freezing

Question 19

Solid to gas is ____________

Answer 19

sublimation

Question 20

Gas to solid is ____________

Answer 20

deposition

Question 21

The ____________ point is the temperature and pressure above which there is no distinction between the phases. This is where the phase boundary between gas and liquid terminate.

Answer 21

critical

Question 22

Something above the critical point is called a ________________ fluid.

Answer 22

supercritical

Question 23

Draw a phase diagram and label

Answer 23

Question 24

The heat of vaporization at the critical point and for all temps and pressures above this point is ________.

Answer 24

zero

Question 25

________________ is the average kinetic energy of particles in a substance.

Answer 25

temperature

Question 26

____________ ____________ is the measure of the total kinetic energy of the particles in a substance

Answer 26

thermal energy

Question 27

________________ measures the average kinetic energy of the particles in a substance

Answer 27

temperature

Question 28

________ is the transfer of energy from one substance to another as a result of their differences in temperature.

Answer 28

Heat

Question 29

The ________ law of thermodynamics implies that objects are in thermal equilibrium only when their temps are equal.

Answer 29

zeroth

Question 30

The heat (q) absorbed or released in a given process is calcualted via what equation?

Answer 30

q = mc∆T

Question 31

Specific heat is what?

Answer 31

The amount of energy required to raise the temperature of one gram of substance by one degree Celsius

Question 32

What is H2O's specific heat?

Answer 32

1 cal/g*K

Question 33

While a glass of water and a pool have the same specific heat, they have different ________ ____________ - the produce mc (mass time specific heat)

Answer 33

heat capacities

Question 34

How to solve for equilibrium temperature?

Answer 34

set q equal to each other

Question 35

Phase change reactions do not undergo changes in temperature. You must use what equation?

Answer 35

q = mL = n∆H | m = mass in g, latent heat = enthalpy of an isothermal process n= mol

Question 36

When going from liquid to solid, change in enthalpy is ________ because heat is removed.

Answer 36

negative

Question 37

When transitioning at the solid-liquid boundary, the enthalpy of ________ must be used to determine heat transferred during the phase change.

Answer 37

fusion

Question 38

When transitioning at the liquid-gas boundary, the enthalpy of ________ must be used to determine heat transferred during the phase change.

Answer 38

vaporization

Question 39

How do you find enthalpy change of a reaction?

Answer 39

∆H_{rxn = Hproducts - Hreactants}

Question 40

What does a positive ∆H_{rxn mean? Negative?}

Answer 40

Positive = endothermic, negative = exothermic

Question 41

Standard enthalpy of ____________ is the enthalpy required to produce one mole of a compound from its elements in their standard states.

Answer 41

formation; ∆H°_f

Question 42

The standard enthalpy of a ____________ is the enthalpy change accompanying a reaction being carried out under standard conditions.

Answer 42

reaction, ∆H°_rxn

Question 43

How standard enthalpy of a rxn calculated?

Answer 43

Difference between the sum of standard heats of formation for the products and sum of standard heats of formation of reactants

Question 44

________ law states that enthalpy changes of reactions are additive.

Answer 44

Hess's

Question 45

Hess's law applies to what?

Answer 45

enthalpy, entropy, and Gibbs free energy -- any state function!

Question 46

Hess's law can also be expressed in terms of bond ____________, aka bond ________________ ____________. This is the average energy that is required to break a particular type of bond between atoms in the gas phase.

Answer 46

enthalpies, bond dissociation energy

Question 47

The standard heat of ________________ is the enthalpy change associated with the combustion of a fuel.

Answer 47

combustion ; Typically occurs during oxygen

Question 48

The ____________ law of thermodynamics states that energy spontaneously disperse from being localized to becoming spread out.

Answer 48

second | entropy

Question 49

____________ is the measure of the spontanoeous dispersal of energy at a specific temperature: *how much* energy is spread out, or *how widely* spread out energy becomes, in a process.

Answer 49

Entropy

Question 50

Gibbs free energy combines what 3 things?

Answer 50

temperature, enthalpy, and entropy

Question 51

The free energy change of reactions can be measured under standard state conditions to yield the ____________ ________ ____________.

Answer 51

standard free energy, ∆G°_rxn