The vapor pressure and enthalpy of vaporization of an unknown substance are measured to be 425.7 torr and 36.8 kJ/mol, respectively at room temperature (298.15 K). Estimate the normal boiling point of the substance at an atmospheric pressure of 760 torr.
States of Matter
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Chemical Reactions and Equations
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The vapor pressure and enthalpy of vaporization of an unknown substance are measured to be 425.7 torr and 36.8 kJ/mol, respectively at room temperature (298.15 K). Estimate the normal boiling point of the substance at an atmospheric pressure of 760 torr.
The Famous Clausius Clapeyron Equation:
Assume Pressures P1 and P2 at Temperatures T1 and T2 respectively. Thus there exists a relationship between these 4 parameters at known value of enthalpy of Vaporization. This relation was put forward by Clausius and Clapeyron which can be mathematically expressed as-
Given-
P2 = 760 torr i.e. atmospheric pressure
P1=425.7 torr
T2 = ? = This is the normal boiling point temperature we need to calculate
T1 = 298.15 K
R = 8.314 J/Kmol
Hvap = 36.8 kJ/mol
since, 1 kJ = 1000 J
thus, Hvap = 36.8 kJ/mol x 1000 = 36800 J/mol
Substitute the values in Clausius-Clapeyron Equation-
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