lecture 7

Question 1

S universe equals what

Answer 1

S system + S surroundings

Question 2

S universe can also be written in terms of gibbs:

Answer 2

S universe = - G // T

Question 3

what’s gibbs at equilibrium or for reversible change

Answer 3

0. or lower than 0

Question 4

using equation G = H -TS,, how do we find the diff parts

Answer 4

H = pro - rea ( x stoichiometry)
S = pro - rea ( x stoichiometry)

make sure the units are the same

Question 5

if S pro - S rea is positive,, what does this mean

Answer 5

the system entropy favours products

Question 6

if H pro - H rea gives a positive number,; what does this mean

Answer 6

the reaction is endothermic

entropy is taken from the surroundings

Question 7

for a gas,, what happens as pressure increases

Answer 7

as pressure increases,, entropy decreases

it becomes more negative

Question 8

what is needed for a reaction to be spontaneous

Answer 8

Gibbs must be negative

Question 9

Gibbs energy change for ideal monatomic gas

Answer 9

G = (5/2) nRT - TS

Question 10

in gibbs equation G = H - TS,, what increases with temperature (when pressure is constant)

Answer 10

S and H both increase with temperature

Question 11

equation that shows how small changes in Pressure and Temp induce changes in G

Answer 11

dG = V dp- S dT

Question 12

if T is constant,, does pressure affect H

Answer 12

nope :)

Question 13

S is always positive,, so a decrease in temp does what to G

Answer 13

decrease in temp = decrease in G

decrease is larger for systems with higher entropy

• S = dG/dT ) p

Question 14

if V is always positive,,, increase in pressure does what to G

Answer 14

increase in pressure increases G

this increase is larger for systems with larger volumes

V = dG/dP ) T

Question 15

grams of smt when u know it’s mr

Answer 15

X gmol-1

where X is the mr

Question 16

when u have mass in gmol-1
what density units should u have

Answer 16

gm3

x1000 to get from dm to m

Question 17

change in G for ice when
T = 273k
density = 917gdm-3
Pressure increases from 1 bar to 2 bars

Answer 17

use dG = Vdp - SdT
but T is constant so
dG/ dP ) T === V

find V (mass / density) and multiply this by pressure to get G

Question 18

gibbs when temp is constant

Answer 18

dG / dP )T = V

using dG = Vdp- SdT

Question 19

Gibbs when pressure is constant

Answer 19

dG = Vdp - SdT

dG/dT )p = -S

Question 20

gibbs of a gas when given temp, pressure change

Answer 20

G = nRT ln(p1/po)

Question 21

what is universal entropy

Answer 21

-G/T

Question 22

when is 🔺H independent of temperature

Answer 22

when specific heat capacity of products and reactants are equal

Question 23

how does gibbs change with increasing pressure

Answer 23

it increases

Question 24

what does gibbs energy do in terms of entropy

Answer 24

reframed entropy changes in terms of energy

Question 25

what must occur for reactions to occur spontaneously

Answer 25

gibbs must be negative,, it must be less than 0

Question 26

what does integrated gibbs helmholtz equation describe gibbs

Answer 26

describes how gibbs energy changes with temperature