If the heat of reaction increases the vapor pressure of the liquid, the reaction is capable of generating pressure in a closed vessel.

• A. True
• B. False
• C. Cannot be determined
• D. Depends on material

Answer: (A)

Vapor pressure in a closed system directly influences the pressure you can build up inside the vessel. The vapor pressure is the pressure exerted by the liquid’s vapor in equilibrium with the liquid at a given temperature. In a sealed container, any vapor that forms adds to the total internal pressure because there’s nowhere for that gas to escape. If a reaction causes the liquid’s vapor pressure to rise, more molecules enter the gas phase or the existing vapor pressure increases. Since the vessel is closed, those additional gas molecules raise the internal pressure, potentially enough to cause overpressure or rupture. So, when the heat of the reaction increases the liquid’s vapor pressure, the reaction is capable of generating pressure in a closed vessel.