Phase changes: If 2.0 g of water at 0.00°C is to be vaporized, how much heat must be added to it? The specific heat of water is 1.0 cal/g ∙ K, its heat of fusion is 80 cal/g, and its heat of vaporization is 539 cal/g.
A) 1100 cal
B) 1100 kcal
C) 1200 cal
D) 1300 cal
E) 1500 cal

Question

Quizplus · Accepted Answer

To vaporize water at 0°C, it must first be heated to 100°C and then vaporized. The heat required to raise the temperature from 0°C to 100°C is 2.0 g * 1.0 cal/g ∙ K * 100 K = 200 cal. The heat required to vaporize it is 2.0 g * 539 cal/g = 1078 cal. Total heat = 200 cal + 1078 cal = 1278 cal, which rounds to 1300 cal.

Phase Changes: If 2