Thermodynamics Flashcards

1
Q

Boyle’s Law

A

p ∝ 1/V

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2
Q

Lussac’s Law

A

V ∝ T (in K)

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3
Q

Charles’ Law

A

p ∝ T

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4
Q

The ideal gas Law

A

pV = nRT

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5
Q

1 bar in Pascals or N m^(-2)

A

1 x 10^5 N m^(-2)

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6
Q

Converting from °C into K

A

+ 273.15

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7
Q

For 2 gases A and B, what are their partial pressures?

A
PA = (nA RT) / V
PB = (nB RT) / V

Total pressure = PA + PB

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8
Q

Assumptions for the ideal gas Law

A

The molecules take up no volume

No interactions between molecules

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9
Q

Van der Waals equation of state and what a and b account for

A

(nRT / V - nb) - (an^2 / V^2)
a corrects for attractive interactions, which would reduce the pressure from an ideal gas
b corrects for volume of molecules, which would increase the pressure from an ideal gas

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10
Q

ΔU =

A

Internal energy change

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11
Q

Internal energy =

A

U(translation) + U(rotation) + U(vibration) + U(electronic)

For an ideal gas we only need to consider U(translation)

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12
Q

The Equipartition principle

A

for each degree of freedom, we get 0.5kT of energy (0.5 RT per mol)
U = 3/2 R

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13
Q

1st Law of thermodynamics

A

ΔU = q + w

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14
Q

What does isochoric mean?

A

Constant volume

–> dV = 0

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15
Q

What does isobaric mean?

A
Constant pressure
(1st law unchanged)
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16
Q

What does adiabatic mean?

A

No heat change

–> Δq = 0

17
Q

What does isothermal mean?

A

Potential and kinetic energy are unchanged

  • -> ΔU = 0 for an ideal gas
  • -> 𝛿U / 𝛿V = 0 (partial derivatives)
18
Q

H =

A

U + pV

19
Q

2nd Law of thermodynamics

A

The entropy change of a system and surroundings increases in the course of spontaneous change
ΔS(tot) > 0

20
Q

Trouton’s Rule

A

The entropy change when a liquid is vaporised:

Δ(vap)S ≈ 85 J K^-1 mol^-1 for most liquids

21
Q

Sign of ΔS for solid –> ions

A

Negative (ions are more ordered)

22
Q

3rd Law of thermodynamics

A

A perfect crystal at 0 K has zero entropy

23
Q

Free energies and when they’re appropriate

A

Gibbs: G = H - TS (for constant P)
Helmholtz: A = U - TS (for constant V)

24
Q

dU =

A

dq + dw = TdS - pdV