122ch11b_001

122ch11b_001 - 20 21 22 23 11.39) Want to determine the...

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23 11.39) Want to determine the amount of heat necessary to convert 75.0 g of ethanol, C 2 H 5 OH, at -120°C (solid) to the vapor phase at 78°C (gas). The best thing to do is to draw a heating curve (figure 11.19 in the textbook). You determine the heat needed in each region. Since heat (enthalpy) is a state function we can add the heat required in each individual step to get the total heat required for the whole process. Given the following data: m.p. -114°C b.p. 78°C ) H fus = 5.02 kJ/mol ) H v = 38.56 kJ/mol s s = sp. ht. of solid = 0.97 J/g C °C (same as J/g C K) s R = sp. ht. of liquid = 2.3 J/g C °C (same as J/g C K) Heat req. or released w/in a state: q = m C s C ) T Heat req. or released for a phase transition: n C ) H (mass C ) H, if in J/g)
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24 11.39) (cont.) 1 mol ? mol C 2 H 6 O = 75.0 g x ------------ = 1.6 2 8 mol C 2 H 6 O 46.06 g q = q heat solid + q fusion + q heat liquid + q vap = (m s C s s C ) T s ) + (n s C ) H fus ) + (m R C s R C ) T R ) + (n R C ) H
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122ch11b_001 - 20 21 22 23 11.39) Want to determine the...

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