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MCAT General Chemistry > Chapter 7: Thermochemistry > Flashcards

Chapter 7: Thermochemistry Flashcards

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1
Q

What is the first law of thermodynamics?

A

∆U = Q - W

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

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2
Q

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

A

isothermal

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3
Q

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

A

Q = W
heat added equals work done by system

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4
Q

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

A

adiabatic

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5
Q

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

A

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

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6
Q

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

A

isobaric

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7
Q

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

A

isovolumetric; ∆U = Q

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8
Q

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

A

Coupling nonspontaneous reactions to spontaneous ones

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9
Q

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

A

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

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10
Q

State functions describe what?

A

The system in equilibrium state

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11
Q

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

A

25°C
1 atm pressure
1 M concentrations

used for kinetics, eq, and thermodynamics

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12
Q

Liquid to gase phase is known as ________________

A

evaporation, or vaporization

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13
Q

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

A

decreases

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14
Q

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

A

above

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15
Q

Gas back to liquid is ____________

A

condensation

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16
Q

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

A

boiling

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17
Q

Transition from solid to liquid is ________

A

fusion, or melting

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18
Q

Liquid to slid is ____________

A

solidification, crystallization, or freezing

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19
Q

Solid to gas is ____________

A

sublimation

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20
Q

Gas to solid is ____________

A

deposition

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21
Q

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.

A

critical

22
Q

Something above the critical point is called a ________________ fluid.

A

supercritical

23
Q

Draw a phase diagram and label

A
24
Q

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

A

zero

25
Q

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

A

temperature

26
Q

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

A

thermal energy

27
Q

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

A

temperature

28
Q

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

A

Heat

29
Q

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

A

zeroth

30
Q

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

A

q = mc∆T

31
Q

Specific heat is what?

A

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

32
Q

What is H2O’s specific heat?

A

1 cal/g*K

33
Q

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

A

heat capacities

34
Q

How to solve for equilibrium temperature?

A

set q equal to each other

35
Q

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

A

q = mL = n∆H

m = mass in g, latent heat = enthalpy of an isothermal process
n= mol

36
Q

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

A

negative

37
Q

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

A

fusion

38
Q

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

A

vaporization

39
Q

How do you find enthalpy change of a reaction?

A

∆Hrxn = Hproducts - Hreactants

40
Q

What does a positive ∆Hrxn mean? Negative?

A

Positive = endothermic, negative = exothermic

41
Q

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

A

formation; ∆H°f

42
Q

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

A

reaction, ∆H°rxn

43
Q

How standard enthalpy of a rxn calculated?

A

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

44
Q

________ law states that enthalpy changes of reactions are additive.

A

Hess’s

45
Q

Hess’s law applies to what?

A

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

46
Q

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.

A

enthalpies, bond dissociation energy

47
Q

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

A

combustion ; Typically occurs during oxygen

48
Q

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

A

second

entropy

49
Q

____________ 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.

A

Entropy

50
Q

Gibbs free energy combines what 3 things?

A

temperature, enthalpy, and entropy

51
Q

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

A

standard free energy, ∆G°rxn

MCAT General Chemistry (12 decks)

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