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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
Tutti i libri di testoBrown 15th EditionCh.13 - Properties of SolutionsProblema 58b
Capitolo 13, Problema 58b

Caffeine (C8H10N4O2) is a stimulant found in coffee and tea. If a solution of caffeine in the solvent chloroform (CHCl3) has a concentration of 0.0500 m, calculate (b) the mole fraction of caffeine in the solution.

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Identify the given data: the molality (m) of the solution is 0.0500 m, which means there are 0.0500 moles of caffeine per kilogram of chloroform.
Calculate the molar mass of caffeine (C_8H_10N_4O_2) by adding the atomic masses of all the atoms: 8 carbon atoms, 10 hydrogen atoms, 4 nitrogen atoms, and 2 oxygen atoms.
Determine the mass of 1 kg of chloroform (CHCl_3) in moles by using its molar mass.
Calculate the total moles of the solution by adding the moles of caffeine to the moles of chloroform.
Find the mole fraction of caffeine by dividing the moles of caffeine by the total moles of the solution.

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Mole Fraction

Mole fraction is a way of expressing the concentration of a component in a mixture. It is defined as the ratio of the number of moles of a specific component to the total number of moles of all components in the solution. For a solution, the mole fraction of a solute can be calculated using the formula: mole fraction = moles of solute / (moles of solute + moles of solvent).
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Concentration

Concentration refers to the amount of a substance (solute) present in a given volume of solution or in a specific mass of solvent. In this case, the concentration of caffeine is given in molality (m), which is defined as the number of moles of solute per kilogram of solvent. Understanding how to convert between different concentration units is essential for solving problems involving solutions.
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Chloroform as a Solvent

Chloroform (CHCl3) is a common organic solvent used in various chemical applications, including the dissolution of organic compounds. It is important to recognize the properties of chloroform, such as its density and molar mass, as these factors influence the calculation of moles of solvent when determining the mole fraction of a solute in a solution.
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