- #1
DiffusConfuse
- 22
- 0
Homework Statement
vapour pressures of a liquid have been measured and fit to the following equation:
Log10 (mmHg) = -3571/T + 6.124
The melting point has been determined to be 392.7 K.
A Cp value given for the liquid is 250 J/mol K
and theΔSvap is 117 J/mol K
Homework Equations
The Attempt at a Solution
1.
Calculate the standard entropy of the liquid at the melting point.
2. Homework Equations
3. The Attempt at a Solution
T1= 392.7 K P1 = 0.8045 mmHg (from the equation, giving the vapour pressure of the LIQUID at the melting point).
T2= 298.15 K P2= 1.052E-3 mmHg
From the Clausius Clapeyron:
ln(0.8045/1.052E-3)= ΔH/R*(1/298.15 K - 1/392.7 K)
ΔH/R = 8221.89
ΔH = 68361 J/mol
ΔH/T = ΔS = 68361/392.7 = 174.07 J/mol K
However the answer is about twice this value