Which of the following is a base?

Which of the following is a base?

• A. Hydrochloric acid
• B. Sodium chloride
• C. Ammonia
• D. Carbon dioxide

Answer: (C)

Bases are substances that accept protons or increase the concentration of hydroxide ions in solution. Ammonia does this in water: NH3 + H2O ⇌ NH4+ + OH-. The formation of OH− raises the solution’s pH, so ammonia acts as a base. The other substances don’t fit this role: hydrochloric acid donates protons and lowers pH, sodium chloride is a neutral salt that doesn’t significantly alter pH, and carbon dioxide dissolves to form carbonic acid, which behaves as an acid rather than a base. In hazmat contexts, recognizing bases helps predict how a substance will react with acids and participate in neutralization processes; ammonia is a weak base that forms ammonium salts when it reacts with acids.

Bases are substances that accept protons or increase the concentration of hydroxide ions in solution. Ammonia does this in water: NH3 + H2O ⇌ NH4+ + OH-. The formation of OH− raises the solution’s pH, so ammonia acts as a base. The other substances don’t fit this role: hydrochloric acid donates protons and lowers pH, sodium chloride is a neutral salt that doesn’t significantly alter pH, and carbon dioxide dissolves to form carbonic acid, which behaves as an acid rather than a base. In hazmat contexts, recognizing bases helps predict how a substance will react with acids and participate in neutralization processes; ammonia is a weak base that forms ammonium salts when it reacts with acids.