Final answer:
When 1 mol of water at 100°C and 1 bar pressure is converted to ice at 0°C, the internal energy change is 34.69 kJ.
Step-by-step explanation:
When 1 mol of water at 100°C and 1 bar pressure is converted to ice at 0°C, there are two steps involved: vaporizing water and then freezing the water vapor.
In the first step, vaporizing water, 40.7 kJ of heat is absorbed from the surroundings for 1 mol of water at 100°C to convert into water vapor at 100°C. In the second step, freezing the water vapor, 6.01 kJ of heat is released as 1 mol of water vapor at 100°C condenses to ice at 0°C.
The internal energy change for this conversion can be calculated by adding the two heats together, taking into account their signs: ΔU = ΔUvaporization + ΔUfusion = (+40.7 kJ) + (-6.01 kJ) = 34.69 kJ.