Question

Which of the following substances would you expect to require the most energy while vaporizing at 1.0 atm pressure?

• A. Neon
• B. Methanol
• C. Ammonia
• D. Water
• E. Benzene

Answer 1

The correct option is D Water

Since $\Delta H_{rxn}$ is maximum from the table i.e. $40.7kJ/mol$ the energy required for vaporising water will be higher than the others.

Enthalpy of reaction ($\Delta H_{rxn}$) is the change in enthalpy when a substance is transformed.

i.e $\Delta H_{rxn}$ = energy required (added) to break the bonds of reactants - energy released to make products bonds

From the table, since $\Delta H_{rxn}$ for water is more than others i.e. 40.7 KJ/mol. Hence water will require most energy while vaporizing at 1 atm.