A Substance Has a Melting Point of 20°C and a Heat

question 34

Multiple Choice

A substance has a melting point of 20°C and a heat of fusion of $3.6 \times 10^4 \mathrm {~J} / \mathrm { kg }$ The boiling point is $150 ^ { \circ } \mathrm { C }$ and the heat of vaporization is $7.2 \times 10^4 \mathrm {~J} / \mathrm { kg }$ at a pressure of one atmosphere. The specific heats for the solid, liquid, and gaseous phases are 600 J/kg ∙ K (solid) , 1000 J/kg ∙ K (liquid) , and 400 J/kg ∙ K (gaseous) . How much heat is given up by $2.80 \mathrm {~kg}$ of this substance when it is cooled from 170°C to 86°C at a pressure of one atmosphere?

• A) 400 kJ
• B) 200 kJ
• C) 300 kJ
• D) 440 kJ
• E) 640 kJ

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