ORP measures oxidation-reduction potential. Which statement is true?

• A. ORP indicates the concentration of dissolved oxygen
• B. ORP measures oxidation-reduction potential
• C. ORP measures pH
• D. ORP predicts electrical conductivity

Answer: (B)

ORP measures the tendency of a solution to gain or lose electrons, which is its oxidation-reduction potential. An ORP sensor outputs a millivolt value that reflects the overall redox activity in the solution, based on the balance of oxidants and reductants present. This is not a direct measure of how much dissolved oxygen is there, nor is it a direct measure of pH or conductivity. Dissolved oxygen can influence redox conditions, but ORP doesn’t quantify oxygen concentration. Likewise, pH is about hydrogen ion activity, and conductivity relates to how well ions move in solution; neither is what ORP directly reports. So the statement that ORP measures oxidation-reduction potential is the true description.