Question

An equimolar mixture of methanol and water is stored at 1 atm pressure. Below what temperature will the mixture exist as a single liquid phase? Above what temperature will it exist as a single gas phase?

Thank you.

Answer 1

The Txy diagram for methanol and water system from literature is shown below

From the problem given day is : mixture is equimolar x=0.5; y=0.5

In the above phase diagram below the lower line both liquids exist as liquids and above the upper curve both exist as vapour, in between two curves mixture exist as both vapour and liquid.

At x=0.5 the below curve temperature is equal to 73°C. Below this temperature both methanol and water exist as liquid

Above curve temperature is equal to 84°C. Above this temperature both methanol and water exist as vapour.