How do dilution and quenching help control hazards?

• A. Dilution lowers concentration; quenching cools or stops the reaction.
• B. Dilution raises concentration; quenching accelerates reaction.
• C. Dilution increases temperature; quenching creates vapors.
• D. Dilution signals an emergency; quenching is optional.

Answer: (B)

Controlling hazards here hinges on reducing what drives the reaction: concentration and temperature. If you dilute a reactive mixture, you lower the amount of reactant present per unit volume, which slows the reaction rate. A slower rate means less heat and gas production at any moment, making runaway scenarios far less likely. Quenching takes a different but complementary approach: it rapidly removes energy or shuts off the reaction pathway, effectively stopping the reaction. This can be done by cooling the mixture or adding a substance that halts the reaction.

Together, dilution lowers the driving force (concentration) and quenching removes the energy input or neutralizes active species, giving you a way to prevent or stop hazardous escalation. Adding more concentrated material or trying to speed up the reaction would increase risk, and suggestions that quenching creates vapors or is optional don’t support hazard control.