Thermodynamics: entropy

  • #1
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Homework Statement



Heat leaks out of a house at the rate of [tex]2.5\times{10^4} \frac{kcal}{h}[/tex]. The temperature inside the house is 21°C and the temperature outside the house is -5°C. At what rate does this process produce entropy.


Homework Equations



[tex]S(A)-S(A_0)=-\frac{\Delta{Q}}{T_1}+\frac{\Delta{Q}}{T_2}=\Delta{Q}\times{(\frac{1}{T_2}-\frac{1}{T_1})}[/tex]


The Attempt at a Solution



Heat flows from the high temp res to the low temp res at a rate of [tex]2.5\times{10^4} \frac{kcal}{h} = 6944.4 \frac{cal}{s} = \Delta{Q}[/tex].

[tex]T_1=21°C=294.15K[/tex]
[tex]T_1=-5°C=268.15K[/tex]

Plugging and chugging I get: [tex]2.29 \frac{cal}{K\times{s}}[/tex], which is wrong.

The answer in the back of the book is [tex]8.2\times{10^3}\frac{cal}{K\times{s}}[/tex].
 

Answers and Replies

  • #2
hage567
Homework Helper
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If you leave your answer in cal/(K x h), you get the book's answer. Maybe they made a mistake?
 
  • #3
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Now I feel stupid for overlooking a such a trivial detail as unit conversions.
 

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