The conductivity meter is calibrated with:

Calibration of a conductivity meter is essential for accurate measurements of ionic concentration in solutions. The choice of standard used for calibration depends on the expected range of conductivity and the specific ions under study.

Potassium chloride (KCl) is widely recognized and often used as a calibration standard for conductivity meters. KCl solutions provide a well-defined relationship between concentration and conductivity due to their complete dissociation in water, which is suitable for a wide variety of applications. The conductivity values for known concentrations of potassium chloride are established and can be referenced for precise calibrations.

In contrast, while other candidates may offer some utility depending on the application, they are less common for this specific calibration purpose. For example, sodium bicarbonate and calcium chloride may complicate the calibration due to their tendency to introduce varying conductivity responses and differing dissociation characteristics. Sodium chloride is another common choice, but in a more dilute form than provided in the given options.

Thus, potassium chloride at the 0.0100 N concentration provides a practical and reliable standard for calibrating conductivity meters, making it the most suitable option in this context.