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
Ch.13 - Solutions
Chapter 13, Problem 67
An aqueous solution contains 36% HCl by mass. Calculate the molality and mole fraction of the solution.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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 volume, as it is based on mass rather than volume. To calculate molality, one must first determine the moles of solute and the mass of the solvent in kilograms.
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Mole Fraction
Mole fraction is a way to express the concentration of a component in a mixture, defined as the ratio of the number of moles of that component to the total number of moles of all components in the mixture. It is a dimensionless quantity and is useful for understanding the composition of solutions. To find the mole fraction, one must calculate the moles of both the solute and the solvent.
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Mass Percent
Mass percent, or weight percent, is a way to express the concentration of a solute in a solution, calculated as the mass of the solute divided by the total mass of the solution, multiplied by 100. In this case, a 36% mass percent of HCl means that there are 36 grams of HCl in every 100 grams of solution. This information is crucial for converting mass to moles and subsequently calculating molality and mole fraction.
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Related Practice
Textbook Question
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Open Question
An aqueous solution contains 5.0% NaCl by mass. How do you calculate the molality and mole fraction of the solution?
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