2.) In lecture we examined the temperature dependence of the phase transition in
ID: 542867 • Letter: 2
Question
2.) In lecture we examined the temperature dependence of the phase transition including and not including the heat capacity as temperature dependent. a.) Using standard thermodynamic tables, evaluate AH. for water at 298.15 K b.) The measured vapor pressure of water is 23.756 torr at 298.15 K. Use the Clausius-Clapyron equation to compute the boiling point of water assuming AHap is temperature independent. Calculate the % error from literature. c) Now, assume that Hvap is temperature dependent and that the heat capacity for vapor is temperature dependent and given below: opH2O(g))-26.06 0.0177T -2.63 x 10 T+2.20 x 10 T J/mol-K C(H2ON)-75.48 J/mol-J Compute the boiling point and calculate a % error. As this is a lengthier polynomial, execute this problem numerically The following is a list of ice vapor pressures at various temperatures. 1.950 2.021 2.093 2.168 2.246 2.326 2.408 2.493 2.581 6.42.672 2.765 2.862 -5.22.962 -10.0 9.6 9.2 -8.8 -8.4 -8.0 7.6 7.2 -6.8 4.8 4.4 3.065 3.280 3.393 3.509 3.630 3.753 3.880 4.012 4.147 4.287 -4.0 3.6 3.2 2.8 2.4 2.0 1.6 -6.0 5.6 0.8 -0.4 0.0 4.579Explanation / Answer
a) From thermodynamic tables Hvap of water at 298.15K = 44 kJ/mol
b) ln (P1 / P2) = Hvap / R [ 1/T2 - 1/T1 ]
Assuming Hvap is temperature independent calculate the BP of water
P1 = 23.756 torr ; T1 = 298.15 K
The boling point is the temperature where the vapor pressure of liquid is 1 atm so
P2 = 760 torr ; T2 = ? K ; Hvap = 44*103 J/mol ; R = 8.314 J/mol
ln (23.756 / 760) = 44*103 / 8.314 [ 1/T2 - 1/298.15 ]
-3.4654 / 5292.2781 = [ 1/T2 - 3.3540*10-3 ]
T2 = 370.48 K
Literature BP of water = 373.15 K
% error = ( | literature value - calc value| / literature value)*100
% error =( |373.15 - 370.48 | / 373.15 )*100 = 0.7153 %
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.