Multicomponent Equilibrium Thermodynamics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 109

3.30 2 The mean activity coefficients of KCl in water at 25 ◦ C are given below:

Molality of KCl Γ ∀

0.1 0.77

0.2 0.72

0.3 0.69

0.5 0.65

0.6 0.64

0.8 0.62

1 0.60

Test whether the above data are in compliance with the Debye-Huckel
limiting law.
3.31 2 State whether the following statements are true or false:
(a) Octanol-water partition constant is a measure of the aqueous activity
of a species.
(b) Excess free energy of dissolution for a large hydrophobic molecule
is positive since the excess enthalpy is always positive.
(c) Methanoldoesnotincreasethesolubilityofdichlorobenzeneinwater.
(d) At equilibrium the standard state chemical potentials for a species i
in air and water are the same.
(e) Fugacity is a measure of the degree to which equilibrium is estab-
lished for a species in a given environmental compartment.
(f) If two aqueous solutions containing different nonvolatile solutes
exhibit the same vapor pressure at the same temperature, the activities
of water are identical in both solutions.
(g) If two liquids (toluene and water) are not completely miscible with
one another, then a mixture of the two can never be at equilibrium.
3.32 2 Chlorpyrifos is an insecticide. It is a chlorinated heterocyclic compound
and is only sparingly soluble in water. Its properties are t m = 42 ◦ C, M =
350.6, log K ow = 5.11, and, K aw = 4.16 × 10 − 3 atm P/mol. Estimate its
vapor pressure using only the given data.
3.33 2 Calculate the infinite dilution activity coefficient of pentachlorobenzene
(C 6 HCl 5 ) in water. It is a solid at room temperature and has a melting
point of 86 ◦ C and a molecular weight of 250.3. It has a log K ow of 4.65.
3.34 1 Match the equation on the right with the appropriate statement on the left.
Only one equation applies to each statement.

Raoult's Law (A) G c + G t

Henry's constant (B) RT Pn γ i

(C) (d PnP / d T) = Δ H/RT 2

Octanol-water partition constant

(D) KC 1 /m

Ionic strength

(E) f i = f i

Gibbs excess free energy

(F) 0.5 3 m i z i

Freundlich isotherm

(G) P i /C i

Clausius-Clapeyron equation

(H) P i /P i
(I) KC
(J) H + TS

Free energy of solution