An electrical heater of power 120 W is immersed in a well-insulated vacuum flask containing liquid nitrogen at its boiling point of 77 K. The specific latent heat of vaporisation of nitrogen is 2.00 × 105 J kg-1.
Assuming all electrical energy is transferred to the nitrogen, what mass of nitrogen is vaporised and escapes from the flask in a time interval of 15.0 minutes15.0\text{ minutes}15.0 minutes?
0.0090 kg0.0090\text{ kg}0.0090 kg
0.54 kg0.54\text{ kg}0.54 kg
1.85 kg1.85\text{ kg}1.85 kg
32.4 kg32.4\text{ kg}32.4 kg