Question

90g of water spilled out from a vessel in the room on the floor. Assume that water vapour behaving as an ideal gas, calculate the internal energy change when the spilled water undergoes complete evaporation at 100°C.

Answer 1

When the water goes from liquid state to vapor state the internal energy decreases but at the same time the temperature remains constant, this usually happens when there are ideal gasses involved.

When we talk about the kinetic gas theory it is not linked with the molecules and in result there is no potential energy.

So the temperature of ideal gas is the only variable which effects the internal energy.

H2O(l) ->H20(s)

△U = △H - △nRT

Value of △H is required to calculate the answer.

But I think there is something missing in the questions I would suggest to check it again and repost your question :)