The amount of heat required to boil away 1.00 liter of water that is already at 100°C can be calculated using the heat of vaporization of water. The heat of vaporization is the amount of heat energy required to convert a substance from a liquid to a gas phase without a change in temperature.
For water, the heat of vaporization is approximately 2.26 x 10^6 joules per liter (J/L). Therefore, to calculate the heat required to boil away 1.00 liter of water at 100°C, you would multiply the volume by the heat of vaporization:
Heat required = Volume × Heat of vaporization
Heat required = 1.00 L × 2.26 x 10^6 J/L
Heat required = 2.26 x 10^6 joules
So, approximately 2.26 x 10^6 joules (2.26 million joules) of heat energy would be required to boil away 1.00 liter of water that is already at 100°C.