How should you combine acid and water according to safety guidelines?

• A. Always add water to acid
• B. Always add acid to water, never water to acid
• C. Add acid slowly with stirring
• D. Add acid slowly to water while cold

Answer: (B)

When diluting acids, heat is released. Pouring water into concentrated acid can cause a rapid, localized heat spike that may lead to splashing or boiling. Adding acid to water lets the water absorb the heat more gradually as the mixture forms, reducing the chance of a dangerous reaction. Therefore, the safe rule is to add acid to water, and do so slowly while stirring (and keep things cool if needed). The other options either reverse the direction or omit the controlled, gradual addition, which increases risk.