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plpg
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Homework Statement
Okay, so I am having difficulties with understanding the concepts around entropy, take this question:
What is the total entropy change for 7 kg of ice melting from -5 C° to 5 C° in room at 5 C°.
Homework Equations
dS=dQ/T
Q =mΔH
m*c*ln(tfinal/tinitial)
c_ice=2
c_water=4
c_air=1
The Attempt at a Solution
Okay, so this is my reasoning so far:
as the ice heats up to zero centigrades, the total change in entropy is given by integrating dS=dQ/T wrt T, and we end up at : m*c*ln(tfinal/tinitial), so 7*2*ln(273.15/(273.15-5)) j/k.
As the ice changes its state to water, the change in entropy is given directly by dS=dQ/T, where dQ is =mdH=7*330=2310 j/k.
When the water heats up from 0 centigrades to 5 centigrades its change in entropy is again given by, 7*4*ln(273.15+5/(273.15)) j/k,
and adding these we get the total entropy change for the melting ice.
Now to the part that I am having big difficulties understanding: the change in entropy of the room. I've read that it is given by m*c_air*((tfinal-tinitial)/tfinal), so in this case this would be negative 7*1*((273.15+5°-(273.15-5°))/(273.15+5°)) j/k.
So adding all these would give me the answer? 7*2*ln(273.15/(273.15-5)) j/k + 2310 j/k + 7*4*ln(273.15+5/(273.15)) j/k - 7*1*((273.15+5°-(273.15-5°))/(273.15+5°)) j/k.
Am i even close to getting this question right?
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