9. Thermodynamics 2

Question 1

What is the equation for dependence of free energy on concentration for a compound in solution?

Answer 1

Ga = Ga° + RT ln [A]

Where Ga= Free energy of component A

Question 2

What is the equation when a solute moves from high concentration to low concentration?

Answer 2

ΔG= RT ln( [A]2 / [A]1 )
Where [A]2= Concentration at LOWER
[A]1= Concentration at HIGHER

Question 3

For a chemical reaction to take place in solution, what does the free energy change depend on?

Answer 3

1) The free energy change for the reaction itself

2) The free energy change due to concentrations of reactants and products

Question 4

Why do you need a standard state? What are the conditions considered to be in standard state?

Answer 4

To ensure that the two factors which free energy change depends on is taken into account.

Standard state:

1) Process is occurring in aqueous solution
2) All components, except the solvent (water) are present at a concentration of 1M
3) pH= 7= [H+] = 10^-7M
4) Unless specified, the temperature= 25°C= 298.2K

The biochemical standard state free energy= G°’

Question 5

What happens when you have moles of many different components?

Answer 5

Must add up individual free energies as each component contributes to overall free energy of the system= Solution + Concentration equation
G = a( GA°’ + RT ln [A] ) + b( GB°’ + RT ln [B] ) + c( GC°’ + RT ln [C] ) + . . .

where a, b and c= moles

Question 6

What is the equation for the free energy change for a reaction?

Answer 6

ΔG = ΔG°’ + RT ln { [Products] / [Reactants] } J mol-1

Make sure to NOT include [H2O] as the standard state is that pH= 7

Question 7

What is the equation for ΔG°’?

Answer 7

ΔG°’ = –RT ln Keq (J mol-1)

IF Keq