In potentiometry, which of the following is considered the standard electrode?

In potentiometry, which of the following is considered the standard electrode?

• A. Hydrogen electrode
• B. Calcium electrode
• C. Potassium electrode
• D. Copper electrode

Answer: (A)

In potentiometry, you need a stable reference potential to compare against the electrode you're studying. The standard hydrogen electrode provides that fixed reference, defined as zero volts under standard conditions (H+ activity = 1 and H2 gas at 1 atm). This creates a universal reference point for measuring other electrode potentials, so any measured potential can be expressed relative to zero. The other electrodes listed—calcium, potassium, copper—do not offer a fixed, universal reference because their potentials vary with ion concentrations and specific conditions, so they serve as working or indicator electrodes rather than the standard reference.

In potentiometry, you need a stable reference potential to compare against the electrode you're studying. The standard hydrogen electrode provides that fixed reference, defined as zero volts under standard conditions (H+ activity = 1 and H2 gas at 1 atm). This creates a universal reference point for measuring other electrode potentials, so any measured potential can be expressed relative to zero. The other electrodes listed—calcium, potassium, copper—do not offer a fixed, universal reference because their potentials vary with ion concentrations and specific conditions, so they serve as working or indicator electrodes rather than the standard reference.