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Problem 18

Without using Appendix $\mathrm{B}$ , predict the…

Problem 17

Without using Appendix $\mathrm{B}$ , predict the sign of $\Delta S^{\circ}$ for
(a) $\mathrm{H}_{2} \mathrm{S}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \stackrel{1}{8} \mathrm{S}_{8}(s)+\mathrm{H}_{2} \mathrm{O}(g)$
(b) $\mathrm{HCl}(a q)+\mathrm{NaOH}(a q) \longrightarrow \mathrm{NaCl}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
(c) 2 $\mathrm{NO}_{2}(g) \longrightarrow \mathrm{N}_{2} \mathrm{O}_{4}(g)$

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Video Transcript

So we're asked Teoh to determine the sign of entropy change or the Delta s of these various reactions. So to start held on this Mike working Cool. Okay, so, um, of various reactions. So let's start with this one, okay? And so essentially the main focus off, actually, before I say that what I think is very important about this problem is that it it is. What it specifies is that you know a lot of his appendix B. And if you don't know already, Appendix B basically gives you all the Delta s values of thes, thes thes, countless thes compounds here, okay? And so you can calculate them if you wanted to, but it's completely unnecessary and is a skill that you must learn that you should be able to determine on the sign of this about have me to do the calculations. Okay, so without further ado, So in this reaction, we have ah, the hydrogen sulfide and reacts with ah have a mole of oxygen gas. And if yields when eight moles of of sulfur solids over and gashes water or di hydrogen monoxide. Okay. So, essentially, the would you have to know is that the interviewer. The randomness of a solid is very little is basically zero and compared Okay, it's not basically zero. It's just insignificant in this in this calculation, and comparison to that of gas and gas is much more random, as much more entropy. So much more that we can basically discount solid. Okay, when you're when it's what if, if you comparing the entropy of solvent and guys, it's always gonna be cast. I don't know of any other obsession except exceptions. So these black dots here are what is representing the entropy of each. If your species ourselves. Yeah, each of these species. So we have the hundreds sulfide right here, and we have the oxygen guys here and half oxygen. So after the size of circle and little tiny dot here, that is the solid sulphur. And this is the cash is water. So I see intel. There's much more randomness here or this. There's much more over here. It's It makes sense because you have more moles of gas. Do you have 1.5 months of gas? You have one mole of gas here. Obviously, this is more understanding more randomness. Thus, this is a decrease in entropy, and thus this is a negative. Okay, the sign is negative. So in this reaction we have, um And as the basic reaction between hydrochloric hydrochloric acid and sodium eye drops a building Sweden chloride ions in a solution of water or in a in water. So in miss diagram here, never at the black ones of the black dots here, that is the ah, hydrogen on our side. Yeah, that is the 100. And the red is the chlorine, and the green is a sodium in the blue is the hydroxide okay, that's over here on the left side, here and essentially. So when you are separately, them don't We have four different islands in solution. But when you combine them together, you only have two ions in solution. And this we're just assuming that this is all you know, perfect. Anyways, you only have to science and solutions. So what happens to the other? I Inslee obviously turned into water and that water becomes part of the solution that the entire thing was already in because the only way the best way for these to react is in solution. And that is what is indicated by the angriest simple here. Anyway, So we have to two species that are in solution here and your four species that are in solution here and they're separated. So, uh, there's so you could probably say that this is more or so. This is more random, This one. You have four here and you have to hear help. That's kind of clear. I hope this is clear that this is more randomness. In that case, that this is more randomness. This is less randomness or less entropy. Then this is a decrease in entropy, and thus the Delta s signed for this reaction is negative. That's green, apparently. And so for this one, this person was like the 1st 1 kind of have to most of gas from a one bowl of guests. And so, to most guys for act one mole against and honestly, more mostly gas take up more space. There's more randomness. And when it's at one, well, I guess that's some randomness. Just not is just not as much as the two most gas it's and that the game we're playing here is this about phases. It's more about just moles when you have more something you obviously have More random. That's more ways to organize that. That something. So therefore, in this case, this is another decrease in entropy or a negative sign for a negative. Delta s here. And the thing is what you were what you should know is that, um from the molecules themselves, if this was just a one mole of nitrogen dioxide, then there actually be Maurin Tribune this side because you have a bigger molecule, it can change it or not. We can change. You can, uh, shape itself in our shape itself. It can appear differently, can take much more permutations. It can, Uh, yeah, I have much more permutations and rearrange itself in different orientations. There we go. Uh, then the nitrogen dioxide. So hopefully that's clear, that this is negative and this is enough that I could be that all negative And it's because mainly because of the most of both most every eight moles that we're dealing with and specific faces that we're dealing with