### ques 31

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How can you calculate dS in pblm 31 in the text without knowing the final temperature? How do you use the specf. heat capacity to do the calc?

-- Anonymous, February 26, 2000

First you must find the final temp by setting heat loss equal to heat gain.

(3.0 mol)(75.3 J/mol C)(final Temp - 0 C) = (1 mol)(75.3 J/mol C)(100 C - final Temp) solve this equation for final Temp final Temp = 25 C= 278 K

Now use delta S =nC ln(final temp/initial temp) to get the delta S

you have to do this for the heating of the 3 mol of water and the cooling of the 1 mol of water.

delta S of heating 3 mol: (3.0 mol)(75.3 J/mol K) ln(298 K/273 K) obtaining 19.8 J/K

you do this calculation for the cooling of 1 mol of water, obtaining -16.9 J/K as the delta S for cooling

delta S total is the sum of both of these delta S's, giving delta S total equal to 2.9 J/K.

Let me know if you need more help.

-- Anonymous, February 26, 2000

There is also an answer to your question if you read the BB question: Homework questions 31 and 32 chapter 10

-- Anonymous, February 27, 2000