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The following information is given for bismuth at 1atm: boiling point = 1.627 ti

ID: 482614 • Letter: T

Question

The following information is given for bismuth at 1atm: boiling point = 1.627 times 10^3 degree C Delta H_vap(1.627 times 10^3 degree C) 822.9 J/g melting point = 271.0 degree C Delta H_fus(271.0 degree C) - 52.60 J/g specific heat solid = 0.1260 J/g degree C specific heat liquid 0.1510 J/g degree C A 34.30 g sample of liquid bismuth at 468.0 degree C is poured into a mold and allowed to cool to 20.0 degree C. How many kJ of energy arc released in this process. Report the answer as a positive number. _ kJ

Explanation / Answer

in this proccess there are first temperature (change 468.0 0C to 271.0 0C) and phase change (liquid to solid) then a temperature change (below 271.0 0C).

q = (34.30 g) (468.0 °C - 271 oC) (0.1510 J g¯1 °C¯1) = 1020.3221 J = 1.02 kJ

phase change

q = (52.60 J/g) (34.30 g ) = 1804.18 J = 1.804 KJ

temperature change in solid

q = (34.30 g) (271.0 °C -20.0 oC) (0.1260 J g¯1 °C¯1) = 1084.77 J = 1.084 kJ

total energy released = 1.084 KJ +1.804 KJ + 1.02 KJ

q = 3.908 kJ (rounded to the appropriate number of significant figures)