have 500.0 g of water at 50.0 ◦C, how much energy would it take to turn it all into water vapor at 1 atm (Lf = 334 J/g and Lv = 2,260 J/g)?

Energy needed to change 500.0 g of water from 50.0 °C to 100.0 °C
= m c ΔT
= (500.0 g) × (4.184 J/g°C) × [(100.0 - 50.0) °C]

Energy needed to change 500.0 g of water to vapor at 100 °C
= m Lv
= (500.0 g) × (2260 J/g)

Total energy needed
= (500.0 × 4.184 × 50 + 500.0 × 2260) J
= 1230000 J
= 1230 kJ