Which chemical is added dropwise to Zamboni solution to alkalinize it?

• A. Water
• B. 2.52% aqueous sodium hydroxide
• C. Sodium chloride
• D. Hydrochloric acid

Answer: (B)

Alkalinizing a solution means raising its pH by adding a base, and you do this dropwise so you can monitor and stop at the exact target pH without overshooting. The only substance here that serves as a base to raise pH in a controlled way is sodium hydroxide, and used as a 2.52% aqueous solution it provides a defined, strong base that can bring the Zamboni solution to the desired alkaline range. Water would not reliably raise the pH, and in many cases would only dilute the solution. Sodium chloride is just a neutral salt and does not alkalinize. Hydrochloric acid would lower the pH, not raise it.