How much heat (in calories) must be applied to a 100 mL beaker filled with boiling water in order to vaporize the water?

540

5.4 x 104

800

8,000

The latent heat of vaporization of water is 540 cal/g/°C. The amount of water is 100 mL. Since the density of water is 1 g/mL, this is equivalent to 100 g. Thus,

540 cal/g/°C * 100 g = 54,000 cal

The answer is 5.4 x 10^4 cal.