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Ch.13 - Properties of Solutions
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.13 - Properties of SolutionsProblema 49a
Capitolo 13, Problema 49a

The density of acetonitrile (CH3CN) is 0.786 g/mL and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by dissolving 22.5 mL of CH3OH in 98.7 mL of CH3CN. (a) What is the mole fraction of methanol in the solution?

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Calculate the mass of methanol (CH_3OH) using its volume and density: \( \text{mass} = \text{volume} \times \text{density} \).
Calculate the mass of acetonitrile (CH_3CN) using its volume and density: \( \text{mass} = \text{volume} \times \text{density} \).
Convert the mass of methanol to moles using its molar mass: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \).
Convert the mass of acetonitrile to moles using its molar mass: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \).
Calculate the mole fraction of methanol by dividing the moles of methanol by the total moles of both methanol and acetonitrile: \( \text{mole fraction} = \frac{\text{moles of methanol}}{\text{moles of methanol} + \text{moles of acetonitrile}} \).

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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. This concept is crucial for calculating the mole fraction of methanol in the solution, as it allows us to quantify the relative amount of methanol compared to acetonitrile.
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00:36
Mole Fraction Formula

Density and Volume Relationship

Density is defined as mass per unit volume and is a key property of substances. In this problem, the densities of acetonitrile and methanol are provided, which allows us to convert their volumes into masses. Understanding how to use density to find mass is essential for determining the number of moles of each component, which is necessary for calculating the mole fraction.
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Relationship of Volume and Moles Example

Calculating Moles from Mass

To find the number of moles of a substance, one can use the formula: moles = mass (g) / molar mass (g/mol). This concept is important in this question because, after determining the masses of methanol and acetonitrile from their respective volumes and densities, we need to convert these masses into moles to compute the mole fraction of methanol in the solution.
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03:12
Molar Mass Calculation Example
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Domanda del libro di testo

The density of acetonitrile (CH3CN) is 0.786 g/mL and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by dissolving 22.5 mL of CH3OH in 98.7 mL of CH3CN. (b) What is the molality of the solution?

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Domanda del libro di testo

The density of acetonitrile (CH3CN) is 0.786 g/mL and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by dissolving 22.5 mL of CH3OH in 98.7 mL of CH3CN. (c) Assuming that the volumes are additive, what is the molarity of CH3OH in the solution?

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Ascorbic acid (vitamin C, C6H8O6) is a water-soluble vitamin. A solution containing 80.5 g of ascorbic acid dissolved in 210 g of water has a density of 1.22 g/mL at 55 °C. Calculate (d) the molarity of ascorbic acid in this solution.

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Domanda del libro di testo

Ascorbic acid (vitamin C, C6H8O6) is a water-soluble vitamin. A solution containing 80.5 g of ascorbic acid dissolved in 210 g of water has a density of 1.22 g/mL at 55 °C. Calculate (c) the molality,

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Domanda del libro di testo

Ascorbic acid (vitamin C, C6H8O6) is a water-soluble vitamin. A solution containing 80.5 g of ascorbic acid dissolved in 210 g of water has a density of 1.22 g/mL at 55 °C. Calculate (a) the mass percentage,

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