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There are numerous methods for indicating the concentration of a solution, one of which is the mole fraction. A mole fraction is a concentration unit. The mole fraction, which is symbolized by “Χ,” measures the relative quantity of solute and solvent in the solution.
The mole fraction is defined as the number of moles of a certain component in a solution divided by the total number of moles in the solution.
The formula for the Mole Fraction
Consider a solution that contains two compounds A and B; the mole fraction of each substance is as follows:
Solute mole fraction = (Moles of Solute) / (Total number of moles of the solutes and the solvent).
(mol A) / (mol A + mol B) = XA
And
(mol B) / (mol A + mol B) = XB
Points to remember:
- The total of all the mole fractions contained in the given combination equals one.
- XA + XB equals 1.
- When the mole fractions are multiplied by 100, the mole percentage is obtained.
- Mole fraction is a dimensionless and unitless term.
- The dimensionless mole fraction scale has the benefit that, in the absence of reaction, the mole fraction of chemical substance R is independent of temperature and pressure. The use of the mole fraction allows calculations to be conducted for gas mixtures.
Molar mixing ratio:
The molar mixing ratio is used to describe the mixing of two or more ratios.
The mole fraction only reflects a subset of molecules. Because distinct molecules have different masses, the individual fraction and the mass fraction might differ.
Examples:
Some examples to get through you the concept of mole fraction thoroughly:
Example 1: Calculate the mole fraction of acetone in a solution containing 2 moles of benzene, 3 moles of carbon tetrachloride, and 5 moles of acetone.
Solution: Number of moles of acetone = 5 moles
Number of moles of carbon tetrachloride = 3 moles
Number of moles of benzene = 2 moles
Total number of moles in solution = number of moles in acetone + number of moles in carbon tetrachloride + number of moles in benzene
= 5 moles + 3 moles + 2 moles
= 10 moles
Mole fraction of acetone = (Number of moles in acetone) / (Total number of moles in the solution)
= 5 moles / 10 moles
= 0.5
Mole fraction of cabon tetrachloride = (Number of moles in carbon tetrachloride) / (Total number of moles in the solution)
= 3 moles / 10 moles
= 0.3
Mole fraction of benzene = (Number of moles in benzene) / (Total number of moles in the solution)
= 2 moles / 10 moles
= 0.2
Example 2: 30 grams of ethanol and 30 grams of water are combined to make a solution. Calculate the mole fraction for each component.
Solution: The molecular weight of ethanol is fixed at 46.07 g/mol.
The number of moles of ethanol present in the solution = 30 grams / 46.07 g/mol = 0.651 moles.
The molecular weight of water = 18g/mol.
The number of moles of water present in the solution = 30 grams / 18 g/mol = 1.67 moles
Total number moles = 0.651 + 1.67 = 2.321 moles
Mole fraction of ethanol = 0.651 moles / 2.321 moles = 0.28
Mole fraction of water = 1.67 moles / 2.321 moles = 0.72
Example 3: If 0.010 moles of NaCl is dissolved in 100 grams of clean water, calculate the mole fraction of NaCl and H2O.
Solution: The molecular weight of water = 18.0153 grams per mole.
Number of moles of water = 100 grams / 18.0153 grams = 5.56 moles
Mole fraction of NaCl = 0.100 moles / ( 5.56 moles + 0.10 moles)
= 0.100 moles / 5.66 moles
Mole fraction of NaCl = 0.018
Mole fraction of H₂O = 5.56 moles / 5.66 moles
Mole fraction of H₂O = 0.982
The Benefits of Mole Fraction
The following are the benefits of mole fraction:
- The mole fraction has never been temperature-dependent.
- It is not essential to have information on the density of the phase in order to compute the mole fraction.
- In the case of an ideal gas mixture, the mole fraction is represented by the ratio of partial pressure to total pressure.
The Drawbacks of Mole Fraction
There is only one drawback to mole fraction, and that is that it is inconvenient for liquid solutions.
Mole Fraction Properties
The following are the attributes of mole fraction:
- The temperature has no effect on a mole fraction. In contrast to molar concentration, mole fraction does not need knowledge of the densities of the phases involved.
- Unlike other techniques of measurement, a valid combination of mole fractions may be formed by taking the weight of the elements into consideration.
- Because the measure is symmetric (example; x=0.1 and x=0.9), the roles of solute and solvent are reversible in a mole fraction.
- In ideal gases, the mole fraction is defined as the ratio of the mixture’s partial pressure to its total pressure.
- The mole express may be stated as a function component in a ternary mixture.
The number of molecules contained inside one component divided by the overall number of molecules in a particular combination is referred to as the Mole Fraction. When two reactive-natured components are combined, it is highly beneficial. The mole fraction is the ratio of the two components. It is a crucial chapter of Class 11 that will also be required for various competitive examinations like IIT, JEE Mains, and NEET. Understand the notion of mole fraction since it will benefit you later as you progress through the complex concepts and principles of chemistry. Use solved examples to see how this topic has been applied and how to tackle challenges in the exercise wisely.
FAQ’s
What is the Importance of Mole Fraction?
The mole fraction is defined as the number of molecules (or moles) in a single component divided by the total number of molecules (or moles) in the combination. When two reactive components are combined, the mole fraction is important because the ratio of the two components can be comprehended if the mole fraction of each is known.
How do students score in their tests if Mole Fraction is introduced?
Those planning to take engineering and other science-related competitive examinations will need to be familiar with this chapter. If the calculations are understood and implemented correctly, Mole Fraction may be highly rewarding. Going over the solved problems will help students understand how each sum should be approached. They can review Mole Fraction, which is provided on this website, as it will serve as an excellent handbook for them. Students may, in fact, pace themselves and then write down all they have learned from this website. This will boost their writing speed while also revealing how much they have learned.
