Molecular Thermodynamics II

Question 1

Gibbs Phase Rule

Answer 1

F = C - P + 2

where F = degrees of freedom, C = number of components and P = number of phases

Question 2

Clapeyron Equation

Answer 2

dP / dT = ΔS / ΔV = ΔH / TΔV

Question 3

Clausius-Clapeyron Equation

Answer 3

dP / dT = PΔS / RT = PΔH / RT²

Question 4

Linearised Clausius-Clapeyron Plot

Answer 4

d ln(P) / d (1/T) = -ΔH / R

Question 5

Activity

Answer 5

α = P / P₀

where P = pressure in solution and P₀ = pressure in the pure system

Question 6

Activity Coefficient

Answer 6

γ = α / x

If γ > 1 the affinity is weaker
If γ < 1 the affinity is stronger
γ = 1 is ideal

Question 7

Raoult’s Law for Solvent

Answer 7

α = x

when x is approximately = 1

Question 8

Henry’s Law for Solute

Answer 8

α is directly proportional to x

when x &laquo_space;1

P = kₕx

Question 9

Boiling Point Elevation

Answer 9

ΔTb = Kb x m₂

where m₂ = solute molality and Kb is the ebullioscopic constant

Question 10

Freezing Point Depression

Answer 10

-ΔTf = Kf x m₂

where m₂ = solute molality and Kf is the cryoscopic constant

Question 11

Osmotic Pressure (van’t Hoff’s Law)

Answer 11

Π = RTc₂