Junior chemist must prepare 500.0 mL of a stock solution of 1.00 M sodium chloride using solid sodium chloride, deionized water, and laboratory glassware. Accurate preparation of a solution of specific molarity requires several steps. Read each procedural step described below and select all that are correct.

Question

BlackTom AI · Accepted Answer

First, consider the goal: to prepare 500.0 mL of a 1.00 M NaCl solution from solid NaCl.
Option 1: Weigh out the calculated amount of solid to the nearest thousandths of a gram. For 0.500 L at 1.00 M, you need 0.500 mol of NaCl. With a molar mass of about 58.44 g/mol, the required mass is 0.500 × 58.44 ≈ 29.220 g. Weighing to the nearest thousandth of a gram (0.001 g) ensures high accuracy in the mass, which is appropriate for precise molarity calculations. This statement is correct.
Option 2: Fill the volumetric flask with exactly 500.0 mL of deionized water. In accurate volumetric procedures, you typically add a portion of water to dissolve the solid and then bring the solution up to the 500.0 mL mark with more water. Filling the flask with exactly 500.0 mL of water before adding solid would prematurely set the volume and can lead to an incorrect final concentration. This statement is incorrect.
Option 3: Add all the solid to the volumetric flask, add water to the line, and then mix to dissolve. This approach disregards the need to dissolve the solid first and then adjust the volume to the mark. Adding solid and watermarking up to the line would not reliably yield the intended concentration because the dissolved volume and partial dissolution can introduce errors. This statement is incorrect.
Option 4: Use a volumetric flask that contains 500.0 mL when filled to the line. A 500.0 mL volumetric flask is designed for preparing solutions to exactly 500.0 mL when the solution is filled to the line, providing the precise final volume needed for a 1.00 M target in this context. This statement is correct.

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