The normal boiling point of ethanol is 73.2˚C, and its molar enthalpy of vaporization is 41.2 kJmol-1 . (a) What is the change in entropy upon vaporization of ethanol at its boiling point? (b) What is the vapor pressure of ethanol at 4˚C?
The normal boiling point of ethanol is 73.2˚C, and its molar enthalpy of vaporization is 41.2 kJmol-1 . (a) What is the change in entropy upon vaporization of ethanol at its boiling point? (b) What is the vapor pressure of ethanol at 4˚C?
Given : Normal boiling point of ethanol = 73.2 ˚C
And enthalpy of vaporization, ΔHvap = 41.2 KJ/mol = 41200 J/mol (since 1 KJ = 1000 J).
a) The change in entropy upon vaporization at normal boiling point s given by,
where ΔS = change in entropy
T = Temperature in K = 273 + T in ˚C = 273 + 73.2 = 346.2 K
Hence substituting the values we get,
Hence the change in entropy upon vaporization of ethanol at its boiling point is 119 J/K.mol.
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