MediumChemistryHigh School (11–12)SolutionsNumerical

Liquids A and B have vapour pressures of 35.0 kPa and 17.0 kPa when pure, at one temperature…

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

Liquids A and B have vapour pressures of $35.0\ \text{kPa}$ and $17.0\ \text{kPa}$ when pure, at one temperature. A solution with a mole fraction of A of $0.25$ has a measured total pressure of $24.1\ \text{kPa}$ . Find the pressure from Raoult's law and the percentage deviation. Say which kind of deviation it is.

Need a reminder? The key ideaShow

An ideal solution obeys Raoult's law at every composition, with $\Delta_{mix}H = 0$ and $\Delta_{mix}V = 0$ . A positive deviation has a pressure above the Raoult line, a weaker A–B attraction, $\Delta_{mix}H > 0$ and $\Delta_{mix}V > 0$ . A negative deviation is the opposite. The deviation is $\dfrac{P_{measured} - P_{Raoult}}{P_{Raoult}} \times 100\ \%$ .

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

← All Problems

← 12.0 g of a non-volatile compound is dissolved in 90.0 g of water at 298 K…Pure A has a vapour pressure of 30.0 kPa and pure B has 20.0 kPa… →

More onSolutions

Discussion (0)

Loading…