An air mattress is filled with 0.55 moles of air. The air inside the mattress has a temperature pf 295 K and gauge pressure of 3.5 kilopascals

Yeah, but what are you trying to ask?

Answerδh > 0explanationc₆h₆  (s)  → c₆h₆ (l)if you are changing it from a solid to a liquid, you are pretty much melting the solid. this requires heat energy. therefore, the reaction is endothermic (takes in energy); the system enthalpy increases as the reaction proceeds: δh > 0.