Question

Calculate the amount of heat needed to boil 82.3 g of hexane (CH14), beginning from a temperature of - 45.3 oC Round your answer to 3 significant digits. Also, be sure your answer contains a unit symbol ollo x10 Ar

Answer 1

Amount of heat = 48.9 x 10³ J     (or 48.9 kJ)

Explanation

Let H1 be the heat required to raise the temperature of liquid hexane from -45.3 ^oC to boiling point 68.73 ^oC

H1 = (mass hexane) * (specific heat liquid hexane) * (final temperature - initial temperature)

H1 = (82.3 g) * (2.27 J/g.^oC) * (68.73 ^oC - (-45.3 ^oC))

H1 = 21303.2 J

H1 = 21.3 kJ

Let H2 be the heat required to convert liquid hexane to vapor hexane at boiling point

H2 = (moles hexane) * (heat of vaporization hexane)

H2 = (mass hexane / molar mass hexane) * (heat of vaporization hexane)

H2 = (82.3 g / 86.1754 g/mol) * (28.85 kJ/mol)

H2 = (0.955 mol) * (28.85 kJ/mol)

H2 = 27.553 kJ

Total heat required = H1 + H2

Total heat required = 21.3 kJ + 27.553 kJ

Total heat required = 48.853 kJ