Phase Changes: a Substance Has a Melting Point of 20°C

Multiple Choice

Phase changes: A substance has a melting point of 20°C and a heat of fusion of 3.5 × 10⁴ J/kg. The boiling point is 150°C and the heat of vaporization is 7.0 × 10⁴ J/kg at a pressure of 1.0 atm. The specific heats for the solid, liquid, and gaseous phases are 600 J/(kg ∙ K) , 1000 J/(kg ∙ K) , and 400 J/(kg ∙ K) , respectively. The quantity of heat given up by 0.50 kg of the substance when it is cooled from 170°C to 88°C, at a pressure of 1.0 atmosphere, is closest to

A) 70 kJ.
B) 14 kJ.
C) 21 kJ.
D) 30 kJ.
E) 44 kJ.