Which of the following best describes how a stock solution is used in the process of making a dilution?

• A. A measured volume of the stock solution is mixed with solvent to achieve a desired lower concentration.
• B. A stock solution is only used to calibrate instruments and not for making dilutions.
• C. The stock solution is evaporated to increase its concentration before use.
• D. The stock solution is directly used without any modification for all experiments.

Answer: (A)

Verified step by step guidance

1. Understand that a stock solution is a concentrated solution that serves as a starting point for preparing solutions of lower concentration.
2. Recognize that making a dilution involves taking a measured volume of the stock solution and adding solvent (usually water) to decrease its concentration to the desired level.
3. Recall the dilution formula: \(C_1 \times V_1 = C_2 \times V_2\), where \(C_1\) and \(V_1\) are the concentration and volume of the stock solution, and \(C_2\) and \(V_2\) are the concentration and volume of the diluted solution.
4. Use the formula to calculate the volume of stock solution needed (\(V_1\)) for a given desired concentration (\(C_2\)) and final volume (\(V_2\)), then add solvent to reach the total volume \(V_2\).
5. Note that the stock solution is not evaporated or used directly without dilution; it is specifically diluted by mixing with solvent to achieve the required concentration.