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How many grams of steam at 100 deg. C would be required to raise the temperature of 43.6 g solid benzene (C6H6) from 5.5 deg. C to 30.0 deg. C?
Hfus for benzene: 9.87 kj/mol
specific heat for benzene: 1.63 J/g x deg
Hvap for steam at 100 deg. C: 40.7 kj/mol

Could you explain how I would go about solving this?
Thanks!

2007-11-08 13:23:52 · 1 answers · asked by Anonymous in Science & Mathematics Chemistry

1 answers

First, find out the heat needed to melt the benzene and raise the temperature of the liquid to 30.0C. Then find the amount of steam you would have to condense to get that heat, assuming that all of the steam condenses to water at 110C.

Atomic weights: C=12 H=1 O=16 C6H6=78 H2O=18

Let benzene be called B. First, melt the benzene:

43.6gB x 1molB/78gB x 9.87kJ/1molB = 5.52 kJ

Next, raise the temperature of the benzene by 30.0C - 5.5C = 24.5degC temperature difference:

43.6gB x 24.5degC x 1.63J/g-C = 1740 J (three sig figs)

5.52kJ + 1.74kJ = 7.26 kJ

Now calculate the steam needed to furnish that much heat:

7.26kJ x 1molH2O/40.7kJ x 18gH2O/1molH2O = 3.21g H2O (steam)

2007-11-08 13:46:27 · answer #1 · answered by steve_geo1 7 · 0 0

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