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Chem 105 > Unit 4: Thermochemistry > Flashcards

Unit 4: Thermochemistry Flashcards

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1
Q

What is thermochemistry?

A

It is an area of chemistry concerned with heat affects accompanying chemical reactions, energy, and spontaneity.

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2
Q

What is energy (U)?

A

The capacity to do work or produce heat.

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3
Q

What is a system?

A

part of the universe we are studying.

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4
Q

What is surroundings?

A

Everything else in the universe.

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5
Q

What is work (w)?

A

Energy transfer due to moving against a force.

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6
Q

What is heat (q)?

A

Energy transfer due to anything other than work.

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7
Q

What is an open system?

A

Exchange of heat/work & matter between the system & surroundings.

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8
Q

What is a closed system?

A

Exchange of heat/work between the system & surroundings.

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9
Q

What is an isolated system?

A

No exchange of heat/work or matter between system & surroundings.

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10
Q

What is an adiabatic system?

A

Exchange or work between system & surroundings.

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11
Q

What is a state function?

A

They are functions or properties of a thermodynamic system. They do not depend on how that condition was reached.

P, V, T, n, and U are state functions.

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12
Q

Are heat and work state functions?

A

No

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13
Q

What is the first law of thermodynamics?

A

The total energy of a system remains constant, even if it is converted from one form to another.

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14
Q

What does internal energy (U) consist of?

A
  • Transitional energy (motion)
  • Energy stored in the bonds
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15
Q

What happens if delta U > 0?

A

Energy of system increases.

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16
Q

What happens if delta U < 0?

A

Energy of system decreases.

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17
Q

What happens if q > 0?

A

System absorbs heat (endothermic)

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18
Q

What happens if q < 0?

A

System releases heat (exothermic)

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19
Q

What happens if w > 0?

A

Work done ON the system by surroundings.

20
Q

What happens if w < 0?

A

Work done BY the system.

21
Q

What are some extensive properties?

A

Heat and heat capacity

22
Q

What are some intensive properties?

A

Temperature, specific heat capacity, and molar heat capacity

23
Q

What quantities does heat depend on?

A
  • Temp change of a substance
  • Amount of a substance
  • Nature of the substance
24
Q

What is heat capacity, Q?

A

The amount of heat required to change a system temperature by 1 degree.

25
Q

What is specific hear capacity, c?

A

The amount of heat absorbed per unit mass of the material when its temperature increases by 1 degree.

26
Q

What is molar heat capacity, C?

A

The amount of heat required to raise 1 mol by 1 degree.

27
Q

What is the calorimeter?

A

An isolated system where no energy or matter is exchanged with surroundings. Specifically, it is used to measure the heat released during a reaction.

28
Q

What are the two most common types of pressure-volume work?

A
  1. Work done BY a gas (expansion)
  2. Work done TO a gas (compression)
29
Q

What happens when the Pext < Pint?

A

Gas will expand, forcing the piston to perform work on its surroundings.
Vi < Vf

30
Q

What happens when the Pext > Pint?

A

Gas will be compressed, and the surroundings will perform work on the system.
Vi > Vf

31
Q

What is enthalpy (H)?

A

The measure of energy in a thermodynamic system.

32
Q

What is entropy (S)?

A

It is a measure of how energy is distributed to, from, or within a system as a function of temperature.
It is closely related to probability.

33
Q

Does the entropy of a system increase if the kinetic energy of a system is increased?

A

Yes , the higher the KE, the more motion, which means more disorder.

34
Q

What is the second law of thermodynamics?

A

All spontaneous processes produce an increase in the entropy of the universe.

35
Q

What is the third law of thermodynamics?

A

The entropy of a pure, perfect crystal at 0K is 0. ( There is no disorder in a perfect system with no atomic motion)

36
Q

What happens if heat is transferred from the surroundings?

A
  • Tsur decreases
  • Ssur < 0
37
Q

What happens if heat is transferred to the surroundings?

A
  • Tsur increases
  • Ssur > 0
38
Q

What is free energy (G)?

A

It is used to determine how systems change and how much work they can produce.

39
Q

What happens if G < 0?

A

The reaction is spontaneous.

40
Q

What happens if G = 0?

A

The reaction is in equilibrium.

41
Q

What happens if G > 0?

A

The reaction is not spontaneous.

42
Q

What happens |H| > |TS|?

A

The reaction is enthalpy driven.

43
Q

What happens |H| < |TS|?

A

The reaction is entropy driven.

44
Q

What are the x and y components, what is the equation, of temperature dependence graph?

A

x = 1/T
y = lnK
lnK = - H/R 1/T + S/R

45
Q

What is an intensive property?

A

Properties that DO NOT depend on quantity or mass.

46
Q

What is an extensive property?

A

Properties that DO depend on quantity or mass.

Chem 105 (5 decks)

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