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MCAT gen chem > Thermochemistry > Flashcards

Thermochemistry Flashcards

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1
Q

What are isolated systems?

A

they exchange neither matter nor energy with the environment.

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2
Q

What are closed systems?

A

They exchange energy, but not matter with the environment.

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3
Q

What are open systems?

A

they exchange both energy and matter with the environment.

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4
Q

What are Isothermal processes?

A

They are processes that occur at a constant temperature

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5
Q

What are adiabatic processes?

A

exchange no heat with the environment.

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6
Q

What are Isobaric processes?

A

occur at a constant

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7
Q

What are isovolumetric (isochoric) processes?

A

occur at a constant volume

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8
Q

What are state functions?

A

describe the physical properties of an equilibrium state; they are a pathway independent and include pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, and entropy.

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9
Q

What are standard conditions?

A

defined as 298K, 1 atm, and 11 M concentrations. Used for kinetics, equilibrium, and thermodynamics. Do not confuse with (STP) standard temperature and pressure for gas laws.

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10
Q

What is the standard state of an element?

A

it is the most prevalent form under standard conditions; standard enthalpy, standard entropy, and standard free energy

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11
Q

What is fusion (melting) and freezing (crystallization or solidification)?

A

A phase change that occurs at the boundary between the solid and the liquid phases.

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12
Q

What is vaporization (boiling or evaporation)?

A

occurs at the boundary between the liquid and the gas phases

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13
Q

What is sublimation and deposition?

A

occurs at the boundary between the solid and gas phases

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14
Q

What is the critical point?

A

a temp past this, the liquid and gas phases are indistinguishable.

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15
Q

What is the triple point?

A

at this point all three phases of matter exist in equilibrium

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16
Q

What is a phase diagram?

A

fro a system graphs the phases and phase equilibria as a function of temperature and pressure.

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17
Q

What is temperature?

A

scaled measure of the average kinetic energy of a substance.

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18
Q

What is heat?

A

The transfer of energy that results form difference of temperature between two substances.

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19
Q

What is Enthalpy?

A

it is the measure of the potential energy of a system found in the intermolecular attractions and chemical bonds

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20
Q

What is Hess’s law?

A

states that the total change in potential energy of a system is equal to the changes of potential energies of the individual steps of the process.

21
Q

How can enthalpy be calculated?

A

using heat formations, heats of combustion, or bond association.

22
Q

What is entropy?

A

while often thought of as disorder, is a measure of the degree to which energy has been spread throughout a system or between a system and its surroundings. Entropy is a ratio of heat transferred per mole per unit kelvin. Entropy is maximized at equilibrium.

23
Q

What is Gibbs free energy?

A

it is derived from both enthalpy and entropy values for a given system. The change in Gibbs free energy determines whether a process is spontaneous or not.

24
Q

What is Gibbs free energy dependent on?

A

temperature; temp dependent processes, change between spontaneous and non-spontaneous, depending on the temperature.

25
Q

First law of thermodynamics equation

A

ΔU= Q-W . U is the change in internal energy, Q is heat added, and W is work done by system.

26
Q

Heat transfer (no change) eq

A

q = mcΔT m is mass, c is specific heat, and T is change in temp. when thinking of heat think which one is receiving heat and losing heat.

27
Q

heat transfer (during phase change)

A

q=mL . m is mass L is latent heat, a general term for the enthalpy of a isothermal process .

28
Q

Generalized enthalpy of reaction

A

ΔHrxn = H products - H reactants

29
Q

standard enthalpy of a reaction

A

ΔH’rxn = ΣΔH’f products - ΣΔH’f, reactants

30
Q

Bond enthalpy

A

ΔH’rxn = ΣΔH bonds broken- ΣΔH bonds formed

31
Q

Entropy

A

ΔS = Qrev/T . Qrev is the heat that is gained or lost in a reversible process

32
Q

Second law of thermodynamics

A

ΔS universe = ΔSsystem + ΔSsurroundings >0

33
Q

Gibbs free energy

A

ΔG=ΔH- TΔS

34
Q

Standard Gibbs free energy

A

ΔG’rxn =ΣΔG’f,products - ΣΔG’f,reactants

35
Q

Standard Gibbs free energy from equilibrium constant

A

ΔG’rxn = -RTln Keq

36
Q

Gibbs free energy from reaction quotient

A

ΔGrxn= ΔG’rxn +RT ln Q= RT ln Q/Keq

37
Q

Temp and internal energy are..?

A

directly proportional .

38
Q

PV=

A

nRT

39
Q

How can energy be supplied to a non-spontaneous reaction?

A

by coupling non-spontaneous reaction to spontaneous ones.

40
Q

What is calorimetry?

A

The process of measuring transferred heat .

41
Q

What is the zeroth law of thermodynamics?

A

objects that are in thermal equilibrium only when their temperatures are equal.

42
Q

Specific heat is what?

A

defined as the amount of energy required to raise the temperature of one gram of a substance by 1 kelvin or degree Celsius.

43
Q

heat capacity

A

=mc

44
Q

Calorimeter equation

A

q system= -q surroundings mct system= mct surrounding

45
Q

Calculating the the phase changes of ice to gas

A

calculate the heat transfer and the phase changing steps, each step will give a certain amount of energy and the add them all together. Use 1= mcT and q=mL

46
Q

What is bond dissociation energy?

A

the average energy that is required to break a particular type of bond between atoms in the gas phase, and is an endothermic process.

47
Q

What are some combustion reactions?

A

with oxygen, diatomic fluoride, and Hydrogen.

48
Q

How does ΔS and ΔH affect ΔG?

A

ΔG= ΔH-TΔS
if both are positive G is spont at high temp .
if H is positive and S is neg than it is nonspont at all T
If H is negative and S is positive it is spont at all T
If H is negative and S is negative is spont at low temp .

49
Q

Rate of reaction depends on…

A

Ea (activation energy), not G

MCAT gen chem (11 decks)

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