What is a working solution?

• A. A solution only used for calibration standards.
• B. The name given to a chemical solution made for actual use in the lab, usually made from diluting or combining stock or standard solutions.
• C. A solution with unknown concentration.
• D. A solution prepared to measure pH only.

Answer: (B)

A working solution is the actual-use solution prepared for daily lab tasks, typically made by diluting or combining stock or standard solutions to reach a practical concentration for the assay or procedure. This matches the description in the option because it describes a solution prepared for real lab use, not just for calibration or a specific measurement like pH.

Why the other ideas don’t fit: calibration standards are specifically prepared to create a calibration curve, not to be the routine reagent you’re actively using in the experiment. A solution with unknown concentration is typically a sample you’re analyzing, not a prepared working solution intended for general use. A solution prepared to measure pH only refers to buffers or standards used for pH measurement, which is a narrow application and not the general “working solution” used across various tasks.