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Hi.
00:02
So we are to determine which of the given reactions has an entropy change that's greater than zero.
00:09
So first we have to understand the concept of entropy change.
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Entropy is the measure of the disorder or randomness of a system.
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And for a reaction, the entropy change is the change in entropy from reactants to products.
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And generally, entropy change is positive if the products are more disordered than the reactants.
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So what we'll do here is we'll just analyze the states of matter.
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Remember, gases have higher entropy than liquids and solids.
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So an increase in the number of gas molecules usually increases entropy.
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Now let's evaluate the given options.
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I'm just going to write here one for the first reaction.
00:45
We have two moles of c2h6 on the reactant side that's in gaseous phase and seven moles of oxygen gas molecules.
00:58
So that means seven gas molecules in total.
01:00
And then we have, i'm just going to write here seven gas, sorry, seven plus two.
01:09
It's going to be nine moles of gas on the reactant side.
01:16
And then on the product side, we have four moles of co2 gas and six moles of h2o in gase as well.
01:22
So that's four plus six, so ten moles of gas on the product side.
01:30
As you can see, the number of gas molecules has increased.
01:34
Nine from nine to ten.
01:37
So that means the entropy change for this reaction is likely positive because the number of gas molecules has increased.
01:47
So this is positive.
01:51
Let me just erase this.
01:54
So that means it is greater than zero.
02:03
The second option, we have one mole.
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I'm just going to write our here, one mole of gaseous reactant plus one mole of o2, so that's two in total rather.
02:18
Let me just erase this.
02:19
That's two moles of gas on the reactant side.
02:22
And then on the product side, we have one mole of co2 gas and one liquid h2o...