Concept explainers
Calculate the vapor pressure of water over each of the following solutions of glycerol, C3H8O3, at 28°C
(a)
(b) 2.74 m
(c)
(a)
Interpretation:
To calculate vapor pressure of water if mass percent of glycerol is 30.6 %.
Concept introduction:
Formula to calculate moles of a component is −
Mole fraction of a component in a solution can be found out by dividing moles of the component by summation of mole of all components in the solution.
Raoult’s law states that vapor pressure of solvent in a mixture is equal to the product of mole fraction of solvent and vapor pressure of pure solvent.
Where,
Answer to Problem 34QAP
Vapor pressure of water if mass percent of glycerol is
Explanation of Solution
Given:
Vapor pressure of pure water = 28.55 mm Hg at 28 °C.
Given mass percent of glycerol is
So, mass of water is
Moles of each component of the solution are to be calculated as follows:
Mass of glycerol
Molar mass of glycerol
So, moles of glycerol is
Mass of water
Molar mass of water
So, moles of water is
Calculation of mole fraction of water
So, mole fraction of water is
Raoult’s law states that vapor pressure of solvent in a mixture is equal to the product of mole fraction of solvent and vapor pressure of pure solvent.
Where,
Mole fraction of water
Vapor pressure of pure solvent
Vapor pressure of water can be calculated as follows:
Hence, vapor pressure of water is
(b)
Interpretation:
To calculate vapour pressure of water if molality of the solution is
Concept introduction:
Molality is one way to define the concentration of solution. It is the ratio of moles of solute to mass of solvent in kilogram.
Formula of molality is-
Raoult’s law states that vapor pressure of solvent in a mixture is equal to product of mole fraction of solvent and vapor pressure of pure solvent.
Where,
Answer to Problem 34QAP
If molality of the solution is
Explanation of Solution
Given:
Vapor pressure of pure water = 28.55 mm Hg at 28 °C.
Given the molality is
Moles of solute (glycerol) can be calculated as follows:
So, moles of solute (glycerol) is
Moles of solvent can be calculated as follows:
Molar mass of water is
Mass of solvent (water) =1000 g
So, moles of solvent is
Mole fraction of solvent can be calculated as follows:
So, mole fraction of solvent (water) is
Raoult’s law states that vapor pressure of a solvent in a mixture is equal to the product of mole fraction of solvent and vapor pressure of pure solvent.
Where,
Mole fraction of water
Vapor pressure of pure solvent
Vapor pressure of water can be calculated as follows:
Hence, vapor pressure of water is
(c)
Interpretation:
To calculate vapor pressure of water if mole fraction of glycerol is
Concept introduction:
For a solution containing solute (glycerol) and solvent (water), summation of mole fraction is equal to one.
Raoult’s law states that vapor pressure of solvent in a mixture is equal to the product of mole fraction of solvent and vapor pressure of pure solvent.
Where,
Answer to Problem 34QAP
Vapor pressure of water if mole fraction of glycerol is
Explanation of Solution
Given:
Vapor pressure of pure water = 28.55 mm Hg at 28 °C.
Given mole fraction of glycerol
Addition of mole fraction of all components of a solution is equal to one.
So, mole fraction of water is
Raoult’s law states that vapor pressure of solvent in a mixture is equal to the product of mole fraction of solvent and vapor pressure of pure solvent.
Where,
Mole fraction of water
Vapor pressure of pure solvent
Vapor pressure of water can be calculated as follows:
Hence, vapor pressure of water is
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Chapter 10 Solutions
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