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Ch.13 - Solutions
Chapter 13, Problem 64b

A solution is prepared by dissolving 20.2 mL of methanol (CH3OH) in 100.0 mL of water at 25 °C. The final volume of the solution is 118 mL. The densities of methanol and water at this temperature are 0.782 g/mL and 1.00 g/mL, respectively. For this solution, calculate the concentration in each unit. b. molality

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Concentration Units

Concentration can be expressed in various units, including molarity (moles of solute per liter of solution) and molality (moles of solute per kilogram of solvent). Understanding these units is crucial for accurately calculating the concentration of a solution, as they reflect different aspects of solute and solvent relationships.
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Molarity vs. Molality

Molarity is defined as the number of moles of solute divided by the volume of the solution in liters, while molality is defined as the number of moles of solute divided by the mass of the solvent in kilograms. The distinction is important because molarity can change with temperature due to volume expansion, whereas molality remains constant as it depends solely on mass.
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Density and Volume Calculations

Density is the mass per unit volume of a substance, and it is essential for converting between mass and volume. In this problem, the densities of methanol and water allow for the calculation of the mass of each component, which is necessary for determining molality, as it requires the mass of the solvent.
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Density Concepts
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Describe how to prepare each solution from the dry solute and the solvent. c. 125 g of 1.0% NaNO3 solution by mass

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For a solution prepared by dissolving 28.4 g of glucose (C6H12O6) in 355 g of water with a final volume of 378 mL, calculate the concentration in each unit: a. molarity, b. molality, c. percent by mass, d. mole fraction, e. mole percent.
Textbook Question

A solution is prepared by dissolving 20.2 mL of methanol (CH3OH) in 100.0 mL of water at 25 °C. The final volume of the solution is 118 mL. The densities of methanol and water at this temperature are 0.782 g/mL and 1.00 g/mL, respectively. For this solution, calculate the concentration in each unit. a. molarity

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Textbook Question

A solution is prepared by dissolving 20.2 mL of methanol (CH3OH) in 100.0 mL of water at 25 °C. The final volume of the solution is 118 mL. The densities of methanol and water at this temperature are 0.782 g/mL and 1.00 g/mL, respectively. For this solution, calculate the concentration in each unit. c. percent by mass

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Textbook Question

A solution is prepared by dissolving 20.2 mL of methanol (CH3OH) in 100.0 mL of water at 25 °C. The final volume of the solution is 118 mL. The densities of methanol and water at this temperature are 0.782 g/mL and 1.00 g/mL, respectively. For this solution, calculate the concentration in each unit. d. mole fraction

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Textbook Question

A solution is prepared by dissolving 20.2 mL of methanol (CH3OH) in 100.0 mL of water at 25 °C. The final volume of the solution is 118 mL. The densities of methanol and water at this temperature are 0.782 g/mL and 1.00 g/mL, respectively. For this solution, calculate the concentration in each unit. e. mole percent

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