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Ch.14 - Solutions
Chapter 14, Problem 59

To what volume should you dilute 50.0 mL of a 3.00 M KI solution so that 25.0 mL of the diluted solution contains 2.55 g of KI?

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1
Calculate the molar mass of KI (potassium iodide) by adding the atomic masses of potassium (K) and iodine (I).
Determine the number of moles of KI in 2.55 g by using the formula: moles = mass (g) / molar mass (g/mol).
Calculate the concentration of the diluted KI solution in moles per liter (M) that would be needed so that 25.0 mL contains the moles of KI calculated in step 2. Use the formula: concentration (M) = moles / volume (L).
Use the dilution equation M1V1 = M2V2, where M1 and V1 are the molarity and volume of the initial solution, and M2 and V2 are the molarity and volume of the final solution. Solve for V2, the final volume needed.
Convert the final volume V2 from liters to milliliters if necessary, as the problem may require the answer in milliliters.

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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 calculating how much solute is present in a given volume of solution, which is essential for dilution calculations.
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Dilution

Dilution is the process of reducing the concentration of a solute in a solution, typically by adding more solvent. The dilution equation, M1V1 = M2V2, relates the initial and final molarities and volumes, allowing for the calculation of the required volume of solvent to achieve a desired concentration.
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Mass to Moles Conversion

To relate mass to moles, the molar mass of the solute is used. For potassium iodide (KI), the molar mass is approximately 166 g/mol. This conversion is necessary to determine how many moles of KI correspond to a given mass, which is vital for calculating the required dilution to achieve a specific mass in a certain volume.
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