The energy needed to keep a 75-watt lightbulb burning for 1.0 h is 270 kJ. Calculate the energy required to keep the lightbulb burning for 4.0 h in kilocalories.

Answer 1

Multiply energy for 1 hour by 4.

270 kJ*4=1080 kJ

Convert kJ to kilocalories. (The conversion factor is 4.184)

1080 kJ/4.184 kJ/kcal=258 kcal