2: What makes a reaction go? (thermodynamics)

Question 1

what is the second law of thermodynamics?

Answer 1

in a spontaneous process, the entropy of the UNIVERSE increases

Question 2

∆S(universe) =

Answer 2

∆S(system) + ∆S(surroundings)

S represents entropy changes

+ve ∆S(universe) = spontaneous

Question 3

forming / breaking bonds endo / exo

Answer 3

forming = EXO, heat leaves system
breaking = ENDO, heat input required

Question 4

how does entropy relate to states

Answer 4

entropy = randomness
g > l > s

Question 5

the stronger the interactions between ions, the more…

Answer 5

exothermic (forming bonds = eco)

Question 6

relationship between heat absorbed, temperature and entropy
equation

Answer 6

supplying heat to a hotter object causes a smaller increase in entropy than supplying same amount to cooler object

∆S(surr) = q(surr) / T(surr)

entropy surr = heat absorbed / temp

Question 7

assumption at constant pressure, q(sys) =

Answer 7

∆H, change in enthalpy of the system

Question 8

Equation for Gibbs energy:

Answer 8

∆G = ∆H - T∆S
all properties of the SYSTEM (so we don’t need to worry about surroundings!)

Question 9

∆S(univ) in terms of G and T of system

Answer 9

∆S(univ) = - ∆G(sys) / T(sys)

Question 10

to be spontaneous, change in Gibbs energy is…

Answer 10

negative (opposite of sign for ∆S)

∆G = G(prod) - G(reac)
so products should have lower Gibbs energy than reactants

Question 11

unit for Gibbs energy

Answer 11

Joules