Verified answer

To evaporate 335 grams of ethanol you first find the # of moles of ethanol you have

Ethanols chemical equation is C2H6O

Divide the mass of the ethanol you have by it's atomic weight

335 / 46.068 = 7.27185mol

Since the Hvap = 38.6 kJ/mol and you want to evaporate the entire mass of the ethanol you multiply the amount of moles of ethanol by the Hvap

7.27185 x 38.6 = 280.6934 kJ

So 280.6934 kJ is the heat needed.

Hope this helps!