Which statement best describes liquid junction potential problems?

Which statement best describes liquid junction potential problems?

• A. The migration of ions to keep the half cells neutral varies greatly causing there to be an unknown potential between the two solutions
• B. They occur only when the solutions have equal ionic strength
• C. They can be eliminated by using standard solutions
• D. They cause a systematic drift that is easily corrected by calibration

Answer: (B)

Liquid junction potential arises at the boundary between two solutions because ions migrate at different rates to balance charge as soon as the two solutions are connected. Each ion has its own mobility, and if the compositions (and concentrations) on the two sides differ, the net movement of positive and negative charges isn’t equal. This unequal migration creates an electric field at the junction, producing a potential difference that you can’t predict without knowing which ions are present and how fast they move. This potential is not determined simply by whether the ionic strengths are equal. Even with equal ionic strength, different ions with different mobilities can produce a junction potential, and it would vanish only if the two sides were effectively identical in composition. Standard solutions or calibration do not eliminate this intrinsic potential; calibration can adjust the overall reading but does not remove the physical junction potential.

Liquid junction potential arises at the boundary between two solutions because ions migrate at different rates to balance charge as soon as the two solutions are connected. Each ion has its own mobility, and if the compositions (and concentrations) on the two sides differ, the net movement of positive and negative charges isn’t equal. This unequal migration creates an electric field at the junction, producing a potential difference that you can’t predict without knowing which ions are present and how fast they move.

This potential is not determined simply by whether the ionic strengths are equal. Even with equal ionic strength, different ions with different mobilities can produce a junction potential, and it would vanish only if the two sides were effectively identical in composition. Standard solutions or calibration do not eliminate this intrinsic potential; calibration can adjust the overall reading but does not remove the physical junction potential.