What is the boiling point of an aqueous solution that has a vapor pressure of 20.5 torr at 25^∘

step 1 that has a vapor pressure of 20 .5 Tor at 25 Celsius degree. And assume that's a non -volatile s

What is the boiling point of an aqueous solution that has a...

Key Concepts

Clausius-Clapeyron Equation

The Clausius-Clapeyron equation provides a relationship between the vapor pressure and temperature of a substance. It is useful for quantitatively analyzing how the vapor pressure changes with temperature, and can be applied to determine the boiling point of a solution by relating the measured vapor pressures at different temperatures.

Raoult's Law

Raoult's Law states that the vapor pressure of a solvent in a solution is directly proportional to its mole fraction. This law explains how adding a nonvolatile solute reduces the vapor pressure of the solution, leading to phenomena such as boiling point elevation.

Boiling Point Elevation

Boiling point elevation is a colligative property observed when a nonvolatile solute is dissolved in a solvent. Because the vapor pressure is lowered, a higher temperature is required to reach the boiling point, meaning the boiling point of the solution is elevated relative to that of the pure solvent.

Boiling Point

The boiling point is the temperature at which the vapor pressure of a liquid equals the external pressure. For solutions, this means that the boiling point is reached when the solution's vapor pressure, which is reduced by any dissolved nonvolatile component, matches atmospheric pressure.

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid (or solid) phase. When a nonvolatile solute is added to a solvent, the vapor pressure of the solution decreases compared to that of the pure solvent.

Transcript

00:01 That has a vapor pressure of 20 .5 tor at 25 celsius degree.

00:05 And assume that's a non -volatile salute.

00:09 All right, so in order to answer this question, we have to recall roth's law says that the partial pressure, the partial vapor pressure of a component of any solution is equal to the product of the mole fraction of the component and the vapor pressure of that component in pure, so we can quantify the vapor pressure of the solution with the road to law by using this equation, p solution equal to more fraction of solution times p0 of the solution.

00:57 And in this equation, p solution is the vapor pressure of the solution.

01:02 This is the more fraction of the solvent water, and p0 is the vapor pressure of the pure, so given that the vapor pressure of the solution, p solution is equal to 20 .5 tor, and the vapor pressure of pure water, p0 is equal to 23 .8 tor.

01:36 So now we can calculate the more fraction of the salute.

01:41 The solvent water equal to pcd, solution divided by p0 of solution and here is solvent not solution so this is equal to 20 .5 divided by 23 .8 and we get the more fraction of solvent equal to 0 .861 so in order to convert the molality we have to assume that we have thousand gram of water.

02:32 So 1 ,000 grams of water divided by the molar mass of water, that's equal to 55 .5 most of water.

02:54 So now the mole fraction can be defined the most of water divided by the the most of water plus the most of solvent, solid.

03:26 So the most of the solute can be calculated as the mole fraction of water is equal to 0 .861, and the most of water is 55 .5, divided by 55 .5 plus in of the solid.

03:45 So we solve for the value in, and we get and equal to 8 .96 moles...

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