[pretzalisa]

One mole of ethanol converts to its vapour at a contant temperature of 298K. deltaH = 43kJmol-1. What is deltaU?

Not even sure what equation to use for this one, tried deltaU= deltaH - delta(nRT) but that didn't ge the right answer.

Thanks

[Yggdrasil]

The correct equation would be ΔU = ΔH - Δ(PV).  Since a liquid takes up much less volume than a vapor, you could assume that the volume of the liquid is essentially zero (or if you're feeling particularly adventurous, you can look up the density).