Formulas Flashcards
(13 cards)
What is the equation for entropy?
S= k lnW
k is the boltzmann constant 1.381x10 -23
W is the number of micro states
What is the equation for the change in entropy related to heat?
^S= qrev/ T dS= drev/ T
qrev is the quantity of heat added reversibly
What is the equation for entropy change for volume change?
^S= nR ln(Vf/Vi)
n is the number of moles
R is the gas constant
You use this equation when you want to calculate the change in entropy for a changing volume
What is the equation for entropy change for temperature change?
^Sm= Cp,m ln(Tf/Ti)
Cp,m is the molar heat capacity
To find ^S, multiply by the number of moles (Sm is the molar entropy)
Use this equation when you want to calculate the change in entropy for a changing temperature
How do you work out the molar heat capacity for a perfect gas at constant pressure?
Cp,m= Cv,m + R
Cv,m is the molar heat heat capacity of a perfect gas at constant volume?
How do you calculate the entropy change of the surroundings
^Ssurr= -^H/T
At constant pressure q=^H so qsystem= ^H
How do you calculate the total entropy change?
^Stotal= ^S(system)+ ^S(surroundings)
How do you calculate Gibbs energy and change in Gibbs energy?
G= H- TS ^G= ^H - T^S
How do you calculate the Gibbs free energy change for changing pressure?
^G= nRT ln(pf/pi)
It the ^G is expressed as molar Gibbs energy you do not need to multiply by the moles
Use this equation when you want to calculate ^G for a changing pressure
How do you calculate the molar Gibbs energy (Gibbs energy for one mole of gas)?
Gm(p)=Gm+ RT ln(p/p)
How do you calculate the change in Gibbs free energy?
^rG= EvGm(products) - E vGm(reactants)
What is the link between change in Gibbs energy and the equilibrium constant?
^rG= -RTlnK
What is the relationship between K and T
Van’t Hoff Isochore
lnK= -^rH/R x(1/T) + ^rS/R
