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### For the reaction depicted in the molecular scenes…

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University of Massachusetts - Lowell

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Problem 29

Without consulting Appendix $\mathrm{B}$ , arrange each group in order of decreasing standard molar entropy $\left(S^{\circ}\right) .$ Explain.
(a) Mg metal, Ca metal, Ba metal
(b) Hexane $\left(\mathrm{C}_{6} \mathrm{H}_{14}\right),$ benzene $\left(\mathrm{C}_{6} \mathrm{H}_{6}\right),$ cyclohexane $\left(\mathrm{C}_{6} \mathrm{H}_{12}\right)$
(c) $\mathrm{PF}_{2} \mathrm{Cl}_{3}(g), \mathrm{PF}_{5}(g), \mathrm{PF}_{3}(g)$

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## Video Transcript

so number 29 minutes because you sort of the various combinations by increasing standard molar entropy. So for eggs to start with A you have magnesium, calcium and barium metallic, um, all basically the same state as it's implied. So basically the only thing that differentiates between the three is there muller mass over their tummy number or their atomic mass. You're all relative to each other anyway, So we have a So, you know, we're looking for the Let's start with looking for the highest entropy. As we know as we have more stuff, we have more entropy. So since only the main thing that differentiates between the three is their amount of stuff for their molar mass, we have a higher muller messed. We have a higher entropy. So that's double. What has the highest Moeller mess. Now? Be very, um, with the average molar mass around 1 37 So it's with them very among the right here. Next we have calcium, which is two spots up on the creative, with the molar mass of 40 just less than Barry. But it's also greater than magnesium, which is at 24 so conveniently throw in order already, which is nice. So when we have increasing more mess and thus increasing moulder in tribute Next for B, we have X ain benzene and cycle haixing again. They're very similar to a, um that the main thing that difference retains between the three is a their name and be their molar mass can molecular formula. So for ah, heck, sane fixing. Here we have C six h 14 fencing of C six, h six and cycle. I'd say with C six, age 12. So see sixes. His is a parent and all three of them. So we're gonna ignore the C six element for now, where the c six component and just compare the different varying amounts of each or hydrogen. Just as we said earlier. More stuff, more entropy. So we in case we have more hydrogen more and should be so thus we have the benzene has the least amount of hydrant. Thus least standard Waller entropy. And what else has this second that is the cycle like saying which has a which has 12 hydrogen on a rather than six and less than 14 which belongs to the hex nehn. So you have these in order we have with increasing standard mold entropy. We have benzene disciple axing to heck saying Next we have ah fast amount of phosphorous die fluoride tranquil, right? I'm not sure how to say that one, but this just say that it is. We have pasta, furs, Penta Florey and phosphorus trifle right? So this one's a little bit different from the other two. Is that yes, the more mass is a major factor, but with P P p f to seal three notes have another element involved as well. And so it's sort of actually looking at PF five pf three. So between these two, like it's like I said in A and B, we have more stuff in pf five plus we have a higher Moeller and repeat in PF five and PF three is lower than that. Okay, so let's look at pf two c 03 s so it is less flurry. But please, the flooring in with the chlorine and chlorine has a higher moulder mass than that Florian So Thus just by having Chloe is just already more more intriguing. Plus because it's a different element. This is just just another situation of random In that case, pf two c 03 has the highest more injury off these three and p F three is the least okay.