The following information is given for antimony at 1 atm: boiling point = 1.440

Question

The following information is given for antimony at 1 atm: boiling point = 1.440 times 10^3 degree C melting point = 631.0 degree C specific heat solid = 0.2090 J/g degree C specific heat liquid = 0.2590 J/g degree C delta H_vap(1.440 times 10^3 degree C) = 1.605 times 10^3 J/g delta H_fus(631.0 degree C) = 161.1 J/g A 33.10 g sample of liquid antimony at 740.0 degree C is poured into a mold and allowed to cool to 21.0 degree C. How many kJ of energy are released in this process. Report the answer as a positive number kJ

Explanation / Answer

heat released when liquid antimony at 744 C is brought to its melting point 631 C

Q1 = mass x specific heat of liquid x temp change

Q1 = m x s x dT

Q1 = 33.1 x 0.259 x (631 - 744)

Q1 = -968.7377 J

now

heat released when liquid antimony at 631 C is converted to solid at 631 C

Q2 = mass x dHfus

Q2 = - 33.1 x 161.1

Q2 = -5332.41 J

now

heat released when solid antimony at 631 C is brought to 21 C

Q3 = m x s x dT

Q3 = 33.1 x 0.209 x ( 21 - 631)

Q3 = -4219.919 J

now

total heat released = Q1 + Q2 + Q2

total heat released = -968.7377 - 5332.41 - 4219.919

total heat released = -10521 J

total heat released = -10.521 kJ

so

10.521 kJ of heat is released

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