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9.19

Posted: Thu Mar 15, 2018 6:11 pm
by Simrina Desar Dis 1H
For question 9.19, why do you have to do 3 steps when calculating change in entropy? Why does it make sense to decrease the temperature again after heating it and doing phase change?

Re: 9.19

Posted: Thu Mar 15, 2018 6:21 pm
by manasa933
The three steps are required as water must be heated to 100 C to vaporize, and then it must be vaporized. Since, they're asking for the final vapor to be at 85 C you need to add another entropy change from the vapor at 100 C to 85 C. All this is required since water doesn't vaporize at a 100 degrees celsius.