Question

Calculate the standard entropy of vaporization of ethanol, C2H5OH, at 285.0 K, given that the molar heat capacity at constant pressure of ethanol vapor is 78.3 J

Answer 1

Answer: The standard entropy of vaporization of ethanol is 0.275 J/K

Step-by-step explanation:

`C_2H_5OH(l)\rightleftharpoons C_2H_5OH(g)`

Using Gibbs Helmholtz equation:

`\Delta G=\Delta H-T\Delta S`

For a phase change, the reaction remains in equilibrium, thus
`\Delta G=0`

`\Delta H=T\Delta S`

Given: Temperature = 285.0 K

`\Delta H=78.3J/mol`

Putting the values in the equation:

`78.3J=285.0K* \Delta S`

`\Delta S=0.275J/K`

Thus the standard entropy of vaporization of ethanol is 0.275 J/K