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Entropy change of Universe - System and Surroundings
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happychappie1700:
Hi Guys,
I wanted to ask you about an example calculation about the entropy change of the universe in regards to whether water will freeze to ice at 5°c ( 278 K ):
ΔSuniv=ΔSsurr+ΔSsys
If we already know that the entropy change of the system for water converting to ice is -22.0 J K-1mol-1 and that the entropy change of surroundings for water converting to ice at 5°c ( 278K ) is 21.6 J K-1 mol-1
Then ΔSuniv=ΔSsurr+ΔSsys:
= 21.6 - 22.0
= -0.4 J K-1mol-1(meaning entropy is reduced in the
universe )
My question is :
where did the - negative sign come from in deducting the 21.6 - 22.0 ?
(when the equation ΔSuniv=ΔSsurr+ΔSsys involves addition )
mjc123:
Because as you said
--- Quote ---we already know that the entropy change of the system for water converting to ice is -22.0 J K-1mol-1
--- End quote ---
Adding -22 is the same as subtracting 22.
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