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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 60

How would you prepare 250 mL of a 0.100 M solution of chloride ions from a 3.00 M stock solution of CaCl2? Spec-ify the glassware that should be used.

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1
Calculate the volume of the 3.00 M CaCl2 stock solution needed to obtain the desired concentration of chloride ions. Use the formula: \( V_1 \times C_1 = V_2 \times C_2 \), where \( V_1 \) is the volume of the stock solution, \( C_1 \) is the concentration of the stock solution, \( V_2 \) is the final volume of the solution, and \( C_2 \) is the desired concentration of chloride ions. Remember that each formula unit of CaCl2 yields two chloride ions.
Convert the volume calculated in the previous step from liters to milliliters, as laboratory measurements are often more practical in smaller units.
Use a volumetric pipette to measure the volume of the stock solution calculated. This glassware allows for precise measurement of the volume of liquid.
Transfer the measured volume of the CaCl2 stock solution into a 250 mL volumetric flask. This flask is used to prepare solutions to a known volume with high accuracy.
Fill the volumetric flask with distilled water up to the 250 mL mark to achieve the final desired volume, ensuring the solution is well mixed.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molarity

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. It is crucial for preparing solutions, as it allows chemists to calculate how much solute is needed to achieve a desired concentration. In this case, understanding molarity helps determine how to dilute the stock solution of CaCl2 to obtain the required concentration of chloride ions.
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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 molarity and volumes of the solution. This concept is essential for calculating how to prepare the desired 0.100 M solution from the 3.00 M stock solution.
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Glassware for Solution Preparation

The choice of glassware is important for accurately measuring and mixing solutions. A volumetric flask is ideal for preparing solutions because it allows for precise volume measurements, while a graduated cylinder can be used for measuring larger volumes. Understanding the appropriate glassware ensures that the solution is prepared accurately and safely.
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