After neutralization of Ni-Cd electrolyte with boric acid, what is the expected pH outcome?

• A. The solution becomes highly acidic
• B. The solution becomes highly basic
• C. The solution remains acidic
• D. The solution becomes neutral or mildly basic

Answer: (D)

Neutralizing an alkaline Ni-Cd electrolyte with boric acid mainly removes hydroxide ions and forms borate species, which are basic in water. Ni-Cd electrolyte is typically a strong base solution (high pH from KOH). When boric acid is added, it reacts with OH- to produce water and borate (B(OH)4−). The borate ions hydrolyze to give a solution that sits around neutral to mildly basic, rather than turning acidic or staying highly basic. In other words, the pH moves from strongly alkaline toward near 7–9, not into the acidic range.