Chemical Thermodynamics (CHMS4208)
BSc, Chemistry - CHMS
Semester: Second Semester
Level: 400
Year: 2018
THE UNIVERSITY OF BAMENDA FACULTY OF SCIENCE
DEPARTMENT OF CHEMISTRY
CA FOR CHMS4208: CHEMICAL THERMODYNAMICS
S2 2017/2018 ACADEMIC YEAR TIME ALLOWED: 2 H
1.
(15 mks) The equilibrium constant for the reaction N
2
O
4
(g) g ⇌ 2 NO
2
(g) at 25°C is K = 0.115 is
related to the degree of dissociation and the pressure P of the system.
(i)
Calculate the change in standard Gibbs free energy, ∆G° at the temperature of the reaction.
(ii)
Establish a relation between K and .
(iii)
Calculate V/n at pressures P = 2 atm, 1 atm and 0.5 atm, assuming that the equilibrium mixture behaves
ideally.
(iv)
What are the corresponding values of V/n if dissociation did not occur.
(v)
Calculate the limit of the compressibility factor Z as P tends towards zero.
2.
(10 mks) A mass x of solid aluminium at 180°C is introduced into an adiabatic vessel containing 50 g of
ice at thermal equilibrium at a temperature of -10°C.
a)
By assuming that the heat capacity of the vessel is negligible, calculate a value for x such that when the
final equilibrium is attained at P = 1 atm, 50% of the ice would have vaporised. C
P
(ice) = 2.1 J K
-1
g
-1
,
C
P
(water) = 4.18 J K
-1
g
-1
, C
P
(AI) = 88.0 J K
-1
g
-1
, L
f
(ice) = 333.5 J g
-1
; L
vap
(water) = 2255.2 J g
-1
.
b)
Calculate ∆S. Is this process spontaneous? Justify!
3. (5 mks) Two vessels of same volume at the same temperature are made to communicate such that their
contents (1 mol of nitrogen in one and 2 mol of helium in the other) can mix. If the gases are ideal, calculate the
variation of entropy due to mixing.
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