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Ch.19 - Chemical Thermodynamics

Chapter 19, Problem 3b

b. If energy can flow in and out of the system to maintain a constant temperature during the process, what can you say about the entropy change of the surroundings as a result of this process?

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Hello everyone. So in this video we're given this following statement considering that the temperature of the process is kept constant by along energy to flow in and out of the system. The entropy change of the surrounding will be positive. Is the statement true or false. So going ahead to apply the second law of thermodynamics that states that the total entropy of both a system and surroundings will never decrease. So the process is spontaneous. They are delta. S. Or change of entropy of the universe is equal to the delta S. Of our system plus our delta us of our surroundings which should be greater than or equal to zero. So that just simplifies down to that delta S. Of our universe Is greater than or equal to zero. So if we're going from a ordered state to a disorder state then the delta S of our system should be greater than zero, which means that we have a positive value. Let's go ahead and write this out. So we're going from again ordered to disorder. Then our delta us of this system is greater than zero, indicating that we have a positive value for our delta us. If this is the case then our delta. So then in this case are dealt to us of the surroundings must be a negative number because we're trying to aim for a negative or R zero value. I apologize, a positive R zero value. So then if our reaction is reversible, we have again that the delta s of the universe is equal to your delta s of the system plus the delta us of our surroundings. And that must equal to zero, which indicates that the delta S. Of the system plus the delta us of our surroundings should equal to zero. Moving one of our factors into the other side of our equal sign. We have that the delta S of the system is equal to the negative delta us of our surroundings. Now the process is irreversible. That means that our delta us our universe again that is just equal to our components DELTA S. Of the system plus the delta S. Of our surroundings. And that's going to be greater than zero. Against defined this then we have the delta us of our system being greater than the delta us of our surroundings. But since we already said that our delta as of our system has to be greater than zero. R. Delta us our surroundings must be positive or negative must be negative. So in our case with that being said to answer a question if it's true or false, our statement is false and that's because the entropy change of the surroundings will be negative. Alright and this is going to be my final answer for this problem. Thank you all so much for watching