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Problem 72

Use $\Delta H^{\circ}$ and $\Delta S^{\circ}$ val…

Problem 71

Use $\Delta H^{\circ}$ and $\Delta S^{\circ}$ values for the following process at 1 atm
to find the normal boiling point of $\mathrm{Br}_{2}$ :
$$\mathrm{Br}_{2}(l) \rightleftharpoons \mathrm{Br}_{2}(g)$$

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Video Transcript

So if this reaction roaming liquid becoming groaning gas already looked up at the table. So Delta H is I should note there always given in killed Jules promote felt esses are given jewels per mole, Kelvin. And so, in order to figure out the Delta's is in Delta Ages reaction as a whole. We always use this saying products minus reactive. And so what That means in practice is, for example, dealt age. We're gonna take the value the product sells H 30.9 minus the delta, uh, ish the reaction or of the reaction zero. So we have 30.9 villages promote as the overall adult age for the reaction. Nice we have for adults s will do 2 45.4 So, products I wrote that wrong 2 45.4 minus the value for the wrap this 1 52.2 And so that gives us our value for Delta S, which is 93 0.15 Jules, promote Calvin. And now we're gonna use this information with this. React with this equation. Delta G equals Delta H minus T Delta s. And this is the relationship between Delta G of a reaction 18 s. And so if this is that equilibrium, eso it. Let's let's get back to what we're saying. A normal boiling point, um is the state where Delta G is going to be equal to zero. In other words, at the normal boiling point. This reaction, um, is exactly halfway from being a liquid to being a gas. And so we're looking for the temperature. That with the Delta h is adults s is that we just found will make the zero. And so with this zero, we can solve to say Delta H equals t Delta s in the temperature of the boiling times that we're looking for is Delta H over Delta s. And so we can plug in these values. Remember, this isn't jewels. And so the security was so I would say, multiply this by thousands. You get this drools and then you'll get the right answer in Taliban. And that right answer is ah, 300 31.8 held this. I would get used to this sort of questions pretty moment, where you get a reaction where you're looking for ah, boiling point or a melting point or in some way. The question applies that we're looking for a situation where Delta G equals zero. And then from there it's always going to stand as we get set this equal to each other. And the temperature that you're looking for is gonna be equal to Delta H over adults. Ask. So this is a question to get used to think about it. Um, yeah.