Thermodynamics Flashcards
(26 cards)
Internal energy ∆U
- ∆U = q + w
- ∆U = adiabatic work
Work done (W)
W = -P∆V
Work done in isothermal reversible expansion
W= -2.303nRTlog(Pi/Pf)
OR
W=-2.303nRTlog(Vf/Vi)
Enthalpy ∆H
∆H=∆U + ∆nRT
When pressure is increased, equilibrium shifts towards….
Where the number of moles is less
For isothermal rev expansion
- ∆U = 0
- q = -w
What is a bomb calorimeter used for?
To measure the change in internal energy of a reaction at constant volume
∆n₉
∆n₉ = (no: of gas product - no: of gas reactants)
Standard gibbs free energy ∆G
- ∆G = -2.303RTlogK
- ∆G = -RTlnK
∆G°ᵣₑₐ꜀ₜᵢₒₙ
∆G°ᵣₑₐ꜀ₜᵢₒₙ = ∆G°ₚᵣₒₔᵤ꜀ₜ - ∆G°ᵣₑ꜀ₐₜₐₙₜ
Gibbs free energy (∆Gբ) of formation for an element in its standard state
Zero
Open system
Exchange both energy and matter
Closed system
Only exchange energy but not matter
Isolated system
Neither exchange energy nor matter
State variables
On changing any one of these variables… The state of the system changes
Eg: P, V, T, no: of moles
Extensive and intensive properties
- Extensive: depends on the amount of the system.
Eg: total energy, volume, mass etc - Intensive: does not depend on amount
Eg: pressure, density, refractive index etc
Isothermal process
Temp const
∆T = 0
When ∆T=0
- ∆H=0
- ∆U=0
Isobaric process
Pressure constant
∆P=0
Isochoric process
Volume constant
∆V = 0
Adiabatic process
No transfer of heat
∆q = 0
8.314 × 10-³ × 298
2.477
Entropy ∆S
- ∆S = qᵣₑᵥ / T
- ∆S = 2.303nClog(T₂/T₁)
- ∆S = Sp - Sr
Heat at constant pressure and heat at constant volume
- constant pressure:
qₚ = ∆H - constant volume:
qᵥ= ∆U
∆T=0
- ∆H = 0
- ∆U=0
