AP Chemistry TSNF Q12/13

Thermodynamically favorable (spontaneous) rxns have…

(-) Delta G

Rxns with … are always thermodynamically favorable?

(-) Delta H and (+) Delta S

If Delta G is (-) then…

Keq is > 1

Rxns that increase the moles of gas have a…

(+) Delta S

Delta H and Delta S are usually…

not given in the same units. Make sure they match when using Delta G = Delta H-T(Delta S)

Delta G equals … at equilibrium

0

When using G=RTlnK,

R = 8.314 and G is in Joules

Sometimes a rxn with a (-)G doesn’t proceed at a measurable rate, this is called…

Under kinetic control, commonly due to high activation energy

Oxidation #’s:

H = +1 (-1 in hydride) O=-2 (-1 in peroxide)

Oxidation always occurs at…

anode, LEO goes GER

Electrons in a battery flow from…

anode to cathode

Salt Bridge:

Cations flow to the cathode, and anins flow to the anode

While a battery is discharged,

the cathode gains mass and the anode loses mass

reversing a reaction, doubling a reaction. (what happens to E)

Reverses sign, nothing.

Ecell equals…

Ered(ger) - Ered(leo) OR Ered + Eox

Half rxn with more +Ered is…

the rxn that takes place in the cathode… GER

when adding two half rxns together…

electrons must cancel out

G=-nFE, so

if G is (-), then E is (+), N = # of electrons transfered

If Q increases

Voltage (Ecell) of battery decreases

Electroplating/Electrolysis calculations:

grams=(molar mass)(amps)(seconds)/(electrons )(faraday’s constant)

g=(MM)(I)(t)/nF