What type of solution is typically used for calibrating a pH meter?

For calibrating a pH meter, a buffer solution is essential because it provides a stable pH value that does not change significantly with dilution or upon the addition of small amounts of acids or bases. Buffer solutions consist of a weak acid and its conjugate base (or a weak base and its conjugate acid) and are designed to resist changes in pH when small amounts of acids or bases are introduced.

When a pH meter is calibrated, the measurements need to be accurate and reproducible. The use of buffer solutions, which are typically available at known and specific pH values (like pH 4, 7, and 10), allows the meter to be adjusted according to these precise pH standards. The calibration process helps ensure that the meter accurately measures the pH of unknown solutions later in experiments.

Using a salt solution, an aqueous solution, or pure water would not provide the ideal conditions for accurate calibration because they don’t have the specific characteristics needed to maintain a stable pH. In summary, buffer solutions are the most appropriate choice for pH meter calibration as they promote accurate and reliable readings across various experimental conditions.