Question

Would you expect a mixture of ethanol/water to have a boiling point pressure greater than or less than the value for ideal solution? Justify your answer.

Answer 1

Boiling point of an azeotropic mixture of water ethanol is less than that of ideal solution and vapor pressure is higher than that of ideal solution as " water-ethanol" forms the minimum boiling azeotrope and deviates positively from the Raoult's law.

As it does not obeys Raoult's law it is called non ideal solution.

By addition of cyclohexane to ethanol, the spaces between the ethanol molecules is occupied by cyclohexane and the some of the hydrogen bonds breaks and hence the boiling point becomes lower than the ideal solution.

P​​​​​​Water > P°water X​​​​​water

and P​​​​​​ethanol > P°ethanol X​​​​Xethanol

As the escaping tendancy of alcohol and cyclohexane from the solution increases, the vapor pressure of the solution increases

Please read the explanation further provided in the picture and feel free for any questions.

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