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Ch.13 - Solutions

Tro 4th Edition

Ch.13 - Solutions

Problem 68

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Chapter 13, Problem 68

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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1

<Step 1: Define molality. Molality (m) is defined as the number of moles of solute (NaCl) per kilogram of solvent (water).>

<Step 2: Calculate the mass of NaCl in the solution. Assume you have 100 g of solution, which contains 5.0 g of NaCl.>

<Step 3: Calculate the mass of the solvent (water). Subtract the mass of NaCl from the total mass of the solution: 100 g - 5.0 g = 95.0 g of water.>

<Step 4: Convert the mass of water to kilograms. Since 1 kg = 1000 g, convert 95.0 g to kg by dividing by 1000.>

<Step 5: Calculate the moles of NaCl. Use the molar mass of NaCl (approximately 58.44 g/mol) to convert the mass of NaCl to moles by dividing 5.0 g by the molar mass.>

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