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Ch.13 - Solutions
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831당신이 사용하는 게 아니라요?교과서 변경
13장, 문제 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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1
Calculate the mass of methanol using its volume and density. Use the formula: mass = volume × density.
Calculate the mass of water using its volume and density. Use the formula: mass = volume × density.
Convert the mass of methanol to moles using its molar mass. Methanol (CH3OH) has a molar mass of approximately 32.04 g/mol. Use the formula: moles = mass / molar mass.
Calculate the mass of the solvent (water) in kilograms, as molality is expressed in moles of solute per kilogram of solvent.
Calculate the molality of the solution using the formula: molality = moles of solute / kilograms of solvent.

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주요 개념

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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.
추천 영상:

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.
추천 영상:

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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가이드 코스
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Density Concepts
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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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