Entropy Variation - System, Neighborhood and Universe

AI Thread Summary
The discussion centers on the concept of entropy change in thermodynamic processes, specifically the equation ΔSuniv = ΔSsys + ΔSneib. It highlights that when ΔSuniv is greater than zero, the process is spontaneous. A key point of confusion arises regarding the relationship between heat transfer and entropy, particularly the equation ΔS = Q/T, which applies only to reversible processes. It is clarified that for irreversible processes, the entropy change is greater than Q/T, leading to the conclusion that ΔSuniv cannot always equal zero, as the heat exchanged between the system and its surroundings is not simply equal and opposite. This distinction is crucial for understanding the spontaneity of processes in thermodynamics.
jaumzaum
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I learned ΔSuniv = ΔSsys + ΔSneib

If ΔSuniv > 0 the process is spontaneous.

But ΔS = Q/T right? Shouldn't Qsys = -Qneib? (The heat released by the system = - heat released by the neighborhood)
I cannot understand why this is wrong!

If it were the case, ΔSuniv would be always zero

Can anyone help me?

[]`s
John
 
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##\Delta S=Q/T## only for reversible processes.For irreversible processes, ##\Delta S>Q/T##.
 
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