An aqueous KNO3 solution is made using 72.5 g of KNO3 diluted to a total solution volume of 2.00 L. Calculate the molality of the solution. (Assume a density of 1.05 g/mL for the solution.)
Ch.13 - Solutions
Chapter 13, Problem 54
To what volume should you dilute 125 mL of an 8.00 M CuCl2 solution so that 50.0 mL of the diluted solution contains 4.67 g of CuCl2?

1
Calculate the moles of CuCl2 in 50.0 mL of the diluted solution using the given mass (4.67 g) and the molar mass of CuCl2.
Determine the molarity of the diluted solution by dividing the moles of CuCl2 by the volume of the diluted solution in liters (50.0 mL converted to liters).
Use the dilution equation, M1V1 = M2V2, where M1 and V1 are the initial molarity and volume, and M2 and V2 are the molarity and volume of the diluted solution, respectively.
Substitute the known values into the dilution equation: M1 = 8.00 M, V1 = 125 mL, and M2 is the molarity calculated in step 2.
Solve for V2, the total volume of the diluted solution, ensuring that all volumes are in the same units (liters or milliliters).
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molarity (M)
Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in moles per liter (mol/L). Understanding molarity is crucial for dilutions and reactions, as it allows chemists to quantify how much solute is present in a given volume of solution.
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Molarity Concept
Dilution Equation
The dilution equation, often expressed as M1V1 = M2V2, relates the molarity and volume of a concentrated solution (M1 and V1) to the molarity and volume of the diluted solution (M2 and V2). This equation is essential for calculating how to achieve a desired concentration after dilution, making it a fundamental tool in laboratory practices.
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Dilution Equation
Mass to Moles Conversion
To relate mass to moles, the formula used is n = m/M, where n is the number of moles, m is the mass of the substance, and M is the molar mass. This conversion is necessary when determining how much solute is present in a solution, especially when given in grams, and is vital for solving problems involving concentrations and dilutions.
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Related Practice
Textbook Question
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Textbook Question
An aqueous KNO3 solution is made using 72.5 g of KNO3 diluted to a total solution volume of 2.00 L. Calculate the mass percent of the solution. (Assume a density of 1.05 g/mL for the solution.)
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A hard water sample contains 0.0085% Ca by mass (in the form of Ca2+ ions). How much water (in grams) contains 1.2 g of Ca? (1.2 g of Ca is the recommended daily allowance of calcium for adults between 19 and 24 years old.)