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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 48c
Capitolo 13, Problema 48c

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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1
Identify the formula for molality: \( m = \frac{\text{moles of solute}}{\text{kilograms of solvent}} \).
Calculate the moles of ascorbic acid using its molar mass. The molar mass of C\(_6\)H\(_8\)O\(_6\) is calculated as follows: \( 6(12.01) + 8(1.01) + 6(16.00) \).
Convert the mass of the solvent (water) from grams to kilograms. Since the mass of water is 210 g, convert it to kilograms by dividing by 1000.
Use the moles of ascorbic acid and the kilograms of water to calculate the molality using the formula from step 1.
Ensure all units are consistent and check calculations for accuracy.

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Molality

Molality is a measure of the concentration of a solute in a solution, defined as the number of moles of solute per kilogram of solvent. It is particularly useful in situations where temperature changes may affect the volume of the solution, as it is based on mass rather than volume. The formula for calculating molality (m) is m = moles of solute / mass of solvent (in kg).
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00:40
Molality

Moles of Solute

To calculate molality, one must first determine the number of moles of the solute, which in this case is ascorbic acid. The number of moles can be calculated using the formula: moles = mass (g) / molar mass (g/mol). The molar mass of ascorbic acid (C6H8O6) is approximately 176.12 g/mol, which is essential for converting grams of ascorbic acid into moles.
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00:27
Mole Fraction Formula

Density and Volume Relationship

Density is defined as mass per unit volume (g/mL), and it plays a crucial role in determining the volume of the solvent when given its mass. In this problem, the density of the solution is provided, allowing us to calculate the volume of the water used. Understanding the relationship between mass, density, and volume is essential for accurately determining the mass of the solvent in kilograms for the molality calculation.
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Relationship of Volume and Moles Example
Pratica correlata
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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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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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. (a) What is the mole fraction of methanol in the solution?

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