lecture 9

Question 1

what is chemical potential

Answer 1

the change in gibbs energy with respect to the number of moles

Question 2

when we mix things,, what must we look out for

Answer 2

we need to see how gibbs changes in terms of the number of moles of each substance being mixed

Question 3

what is chemical potential mathematically

Answer 3

change in gibbs energy with respect to the number of moles

Question 4

symbol for chemical potential

Answer 4

new thingy

long u

Question 5

equation for chemical potential

Answer 5

long u = G / n

n is number of moles

change in gibbs with respect to number of moles

Question 6

what if the system only contains one substance,, what would the chemical potential then be

Answer 6

u = G/n = Gm

chemical potential = molar gibbs energy

Question 7

what is constant in chemical potential

Answer 7

temp, pressure, moles

it’s the gibbs change with respect to number of moles

Question 8

if u = G/n,, what is change in gibbs for a phase change

Answer 8

🔺G = u(a)dn- u(b)dn

equal to ( u(a) - u(b) )dn

so at equilibrium G=0 meaning u(a)=u(b)

this tells us that at equilibrium,, u is the same for all phases

Question 9

u at equilibrium

Answer 9

u is the same for all phases at equilibrium bc Gibbs at equilibrium is 0.

and u=G/n

Question 10

what is G when u mix ideal gases ( a + b)

Answer 10

G = na x ua. +. nb x ub

(sum of moles x chem potential)

Question 11

why is G = ua x na + ub + nb a bad approx for ionic solutions but a good approx for ideal gases

Answer 11

bc ideal gases have no forces of interaction but ionic solutions do.

Question 12

inter component interactions present in ionic solutions but not ideal gases changes what??

Answer 12

it changes the chemical potential (u)
the chemical potential will change with mixture composition.

Question 13

what does the gibbs duhem equation tell us

Answer 13

that if one chemical potential changes,, all the other chemical potential values will also change.

SUM nJ duJ = 0

Question 14

finding the change in gibbs energy when 2 ideal gases mix equation,, and explanation of why ideal gases always mix

Answer 14

G mix = nRT (xa ln(xa) + xb ln(xb) )

Xa being molar fraction

molar fraction is always less than 1,, making Gmix negative,, making their mixing spontaneous!! 💗💗💗💗

Question 15

for an ideal liquid (no interactions) what is the chemical potential of a non pure liquid related to its pure chemical potential (u*a(l))

Answer 15

ua(l) = u*a(l) + RTln(xa)

xa = pa/p*a (raoults law)