Concept explainers
Calculate the vapor pressure of water over each of the following ethylene glycol (C2H6O2) solutions at 22°C
(a)
(a)
Interpretation:
Vapor pressure of water is to be calculated if mole fraction of ethylene glycol is
Concept introduction:
For a solution containing solute (ethylene glycol) 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 product of mole fraction of solvent and vapor pressure of pure solvent.
Where,
Answer to Problem 33QAP
Vapor pressure of water if mole fraction of ethylene glycol is
Explanation of Solution
Given:
Mole fraction of ethylene glycol
Addition of mole fraction of all components of a solution is equal to one.
So, mole fraction of water(solvent) 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,
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:
The vapor pressure of water is to be calculated if mass percent of ethylene glycol is 39.0 %.
Concept introduction:
Formula to calculate moles of a component is −
Mole fraction of a component in a solution can be find 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 product of mole fraction of solvent and vapor pressure of pure solvent.
Where,
Answer to Problem 33QAP
Vapor pressure of water if mass percent of ethylene glycol is
Explanation of Solution
Given:
Vapor pressure of pure water is
Mass percent of ethylene glycol is
Mass percent of ethylene glycol is
It means in
So, mass of water is
Moles of each component of the solution are to be calculated as follows:
Mass of ethylene glycol
Molar mass of ethylene glycol
So, moles of ethylene glycol 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 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:
The vapor pressure of water is to be calculated if molality of the solution is
Concept introduction:
Molality is one way to define 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 33QAP
If molality of the solution is
Explanation of Solution
Given:
Vapor pressure of pure water is
The molality is
Since, the molality is
Moles of solute (ethylene glycol) can be calculated as follows:
So, moles of solute (ethylene glycol) 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
Calculation of mole fraction of solvent is as follows:
So, mole fraction of solvent(water) 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,
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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