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Problem 7

What is the precise definition of entropy? What i…

02:46
Problem 6

Explain the difference between the spontaneity of a reaction (which depends on thermodynamics) and the speed at which the reaction occurs (which depends on kinetics). Can a catalyst make a nonspontaneous reaction spontaneous?

Answer

In thermodynamics, the spontaneity of a chemical reaction refers to the direction in which and extent to which a chemical reaction proceeds. In kinetics, the speed of a reaction refers to how fast a reaction takes place. A reaction may be thermodynamically spontaneous but kinetically slow at a given temperature. Although the rate of a spontaneous reaction can be increased by the use of a catalyst, a nonspontaneous process cannot be made spontaneous by the use of a catalyst. Catalysts affect only the rate of a reaction, not the spontaneity.


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Video Transcript

So the question for this problem is really looking at What's the difference? Treating spontaneous in terms of a reaction and the speed of the reaction? It's only thing about spontaneity. We want to think about this kind of thermodynamic relationship. What were you thinking in terms of energy and the Y axis and you're going from reactors? The products? And so if the state of your products is lower and energy than your reaction, that reaction is spontaneous. So that no matter what is happening, no matter what kind of hill they have to climb, as long as the reactant are higher in energy than the products in their final state. That reaction be spontaneous compared to this one, where the reactant are lower and energy than their products. Final state that Rex was not spontaneous. It could still happen. But you have to put in energy to make it get there. Yes, it is. That's the spontaneity of reaction. Were Thomas Speed of reaction. You're concerned with this intermediate step where they have basically, how does it get there? And that's determined partly by this activation energy. This hill you have to calm initially to get over and there. And so an example of a spontaneous direction is very slow. Is diamonds, um, not lasting forever? And so that reaction looks like this in its turning to another form of carbon. And so it looks like this, but the speed of it takes a very, very long time. So that's a case where this activation energy just is just so enormous that it takes so long for the happen and occur, even though the reaction will and is occurring. And so what is the catalyst Do so a catalyst just takes this activation energy and lowers it, and it can happen. Either way, it can happen in both spontaneous and non spontaneous reactions, and that speeds up the reaction. What it does not do is does not change the position of your reactions and products in this energy diagram. So spontaneous reaction cannot remain on spontaneous in a non spontaneous cannot be made spontaneous with the catalyst only it only fixed the speed of the reaction

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