Final answer:
The change in enthalpy when 250 g of water vapor condenses at 100°C is approximately -564.4 kJ, so the closest answer choice would be D. -565 kJ.
Step-by-step explanation:
The student's question is about determining the change in enthalpy when 250 grams of water vapor condenses at 100°C. We know that the heat of vaporization (or condensation) of water is 40.67 kJ/mol. We use the given heat of vaporization and the mass of water to calculate the total heat released during the condensation.
First, convert the mass of water to moles:
250 g / 18.01528 g/mol = 13.879 moles (approximately).
Next, calculate the total enthalpy change:
13.879 moles * 40.67 kJ/mol = 564.4 kJ (approximately).
Since condensation releases heat, the enthalpy change is negative:
ΔH = -564.4 kJ
Therefore, the correct answer to the question is D. -565 kJ, which is the closest value to the calculated enthalpy change.