What is the vapor pressure in mm Hg of the following solu-tions, each of which contains a nonvolatile solute? The vapor pressure of water at 45.0 °C is 71.93 mm Hg.(b) A solution of 10.0 g of LiCl in 150.0 g of water at 45.0 °C, assuming complete dissociation

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Calculate the moles of LiCl using its molar mass.

Determine the moles of water using its molar mass.

Assuming complete dissociation, calculate the total moles of ions produced by LiCl.

Use Raoult's Law to find the vapor pressure of the solution: \( P_{solution} = \chi_{solvent} \times P^0_{solvent} \), where \( \chi_{solvent} \) is the mole fraction of the solvent.

Calculate the mole fraction of water (solvent) by dividing the moles of water by the total moles of particles in the solution (moles of water + moles of ions from LiCl).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. It reflects the tendency of particles to escape from the liquid phase into the vapor phase. In solutions, the presence of a solute lowers the vapor pressure compared to that of the pure solvent, a phenomenon described by Raoult's Law.

Raoult's Law

Raoult's Law states that the vapor pressure of a solvent in a solution is directly proportional to the mole fraction of the solvent. For a solution containing a nonvolatile solute, the vapor pressure can be calculated by multiplying the vapor pressure of the pure solvent by the mole fraction of the solvent in the solution. This law is essential for understanding how solutes affect the vapor pressure of solvents.

Colligative Properties

Colligative properties are properties of solutions that depend on the number of solute particles in a given amount of solvent, rather than the identity of the solute. These properties include vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure. Understanding colligative properties is crucial for calculating changes in vapor pressure when a nonvolatile solute is added to a solvent.