Question

The human body obtains 955 kJ of energy from a candy bar.? If this energy were used to vaporize water at 100.0 ∘C, how much water (in liters) could be vaporized? (Assume the density of water is 1.00 g/mL.)

Answer 1

The energy to vaporize the water at its normal boilng point (100°C) is the vaporization latent heat.

The vaporization latent heat of water is 2257 J/ g (you can find it in a textbook, tables or internet).

So, with 955 kJ you can vaporize this amount of water:

[995 kJ * 1000J/kJ ] / 2557 J /g = 389.13 g

Use the density to convert to volume: D = M / V => V = M / D

V = 389.13 g / 1.00 g / ml = 389.13 ml, which rounded to 3 significant figures is 389 ml

Answer: 389 ml