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Ch.13 - Properties of Solutions
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Non è quello che usi tu?Cambia libro di testo
Capitolo 13, Problema 42a

A solution is made containing 20.8 g of phenol (C6H5OH) in 425 g of ethanol (CH3CH2OH). Calculate (a) the mole fraction of phenol,

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First, calculate the number of moles of phenol (C6H5OH). Use the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \). The molar mass of phenol is approximately 94.11 g/mol.
Next, calculate the number of moles of ethanol (CH3CH2OH). Use the same formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \). The molar mass of ethanol is approximately 46.07 g/mol.
Add the moles of phenol and the moles of ethanol to find the total number of moles in the solution.
Calculate the mole fraction of phenol using the formula: \( \text{mole fraction of phenol} = \frac{\text{moles of phenol}}{\text{total moles in solution}} \).
Ensure that the mole fraction is a dimensionless number, typically expressed as a decimal.

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Mole Fraction

Mole fraction is a way of expressing the concentration of a component in a mixture. It is calculated by dividing the number of moles of the component by the total number of moles of all components in the solution. This dimensionless quantity provides insight into the relative amounts of substances in a mixture, which is particularly useful in solutions.
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Mole Fraction Formula

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a molecule. Knowing the molar mass is essential for converting between grams and moles, which is necessary for calculating mole fractions in a solution.
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Molar Mass Concept

Solution Composition

Solution composition refers to the relative amounts of solute and solvent in a solution. In this case, phenol is the solute and ethanol is the solvent. Understanding the composition is crucial for calculations involving concentrations, such as mole fraction, as it helps determine how much of each component is present in the solution.
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Solution Components