Tennessee Wastewater Operator Practice Exam

What is used to standardize a pH meter?

1. Distilled water

2. Known buffer solutions

3. Tap water

4. Saline solutions

The correct answer is: Known buffer solutions

The use of known buffer solutions to standardize a pH meter is crucial for obtaining accurate and reliable pH measurements. Buffer solutions have specific, stable pH values, which enable the pH meter to be calibrated correctly. This process ensures that the readings it provides correspond accurately to the pH of the solution being tested. By using buffer solutions with defined pH levels, operators can adjust the pH meter to account for any deviations or measurement errors. Typically, two to three buffer solutions are used—often one that is acidic, one neutral, and another that is basic. This range allows for a full calibration across the scale of pH measurements, thus ensuring the instrument's accuracy throughout its operational spectrum. In contrast, distilled water does not provide a reliable standard for calibration as its pH can change depending on various factors, including exposure to air and the dissolved CO2 content. Tap water and saline solutions similarly lack the stable, definable pH values needed for effective calibration, which is why they are not suitable for this purpose.