Equations Flashcards
Work irreversible
w=- Pex *dV
Work reversible
w= -nRTln(Vf/Vi)
Work free expansion
w= 0
What is an adiabatic process?
No heat is exchanged between the system and the surroundings.
q=0 and dU= w
w=C*dT=-PdV
What is an isothermal process?
Process in which the temperature remains constant.
dT=0=dU [q=-w]
What is the 1st Law of Thermodynamics?
“The energy of an isolated system remains constant”
This is the law of energy conservation
dU=w+q
Heat for system of constant volume
dq=C*dT
dq=dU
w=0
How to link Temp and Volume for adiabatic expansion
Tf=Ti(Vi/Vf)^1/c
c=C/R
Enthalpy from internal energy change
dH=dU+dnRT
Enthalpy from temperature
dH= CdT
Enthalpy at constant temperature
dH=q
Entropy change for an isothermal reversible expansion
dS=nRln(Vf/Vi)
dS= q/T
Entropy change at constant volume
dS=nCln(Tf/Ti)
Carnot efficiency
N=1-Tc/Th
What is the second law of thermodynamics?
“The entropy of an isolated system increases in the course of a spontaneous change”
From liquid to a gas molecules gain increases degrees of freedom (dS>0)
when volume increases dS>0 (system)
