It is best to place the acid dilution in which environment to minimize the exotherm?

• A. ice cold water
• B. Freezer -20°C
• C. Cold water bath
• D. Hot water bath

Answer: (C)

When an acid is diluted, heat is released. To minimize the temperature rise (the exotherm), you want a strong heat sink at a low, stable temperature. A cold water bath provides that: water has high heat capacity and can absorb a lot of heat without a rapid temperature increase, so the surrounding bath keeps the diluted acid from heating up too quickly. It’s practical, safe, and effective for dissipating the exotherm.

An ice-cold environment is even colder, but in practice it’s less reliable and more prone to practical issues (like the bath becoming slushy or changing temperature as ice melts). A freezer would freeze the solution or damage equipment, and a hot water bath would add heat instead of remove it, making the exotherm worse.