### Consider the reaction: 2 \mathrm\ {NO}(g)+\mat…

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Problem 64

Use standard free energies of formation to calculate $\Delta G^{\circ}$ at $25^{\circ} \mathrm{C}$
for each reaction in Problem $62 .$ How well do the values of $\Delta G^{\circ}$ calculated this way compare to those calculated from $\Delta H^{\circ}$ and $\Delta S^{\circ} ?$ Which of the two methods could be used to determine how $\Delta G^{\circ}$ changes with temperature?

PART $\mathrm{A} : \Delta G^{\circ}=69.0 \mathrm{kJ}$
PART $\mathrm{B} : \Delta G^{\circ}=192.2 \mathrm{kJ}$
PART $\mathrm{C} : \Delta G^{\circ}=175.2 \mathrm{kJ}$
PART $\mathrm{D} : \Delta G^{\circ}=-224.4 \mathrm{kJ}$
See explanation.

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## Video Transcript

So this problem is going off of reactions shows a previous problem. And I want you to calculate Delta Jeannot using the values from your appendix of Delta V formation. And so does Jeannot equals the son of and the products see formation of products minus to some of in reactors, which is the moles. The Stoke geometry coefficients terms Delta Gina of reactions. So basically doing products ministry actives and accounting for disturb cam a tree So we can do this for a you're actin are methane ch four as a gas going to see to age six as a gas plus hydrogen gas And so you can look up these values and your textbook And so we get don't g not equals minus 32 Trump c two h six clothes zero for hydrogen minus two to count for the two in front of ch four comes madness 50.5 in this equals 69 killer Jules Um, next reaction to an H three as a gas going to into age four plus age to gas. So you look at these values in your textbook and Dr G equals 1 59.4 plus zero from hydrogen minus two times native, 16.4. And that equals 1 92 point to kill Jules. All right, Percy. Yeah. Into plus O two, hope is a gas going toe to an O. So you have two terms. 87.6, minus zero plus zero. And any girls 1 75 point. To kill Jules or D, you have to k c l 03 as a solid going to to k c E o. Also, it's a solid plus 3 +02 as a guess. And so you have your products, which are three times zero worse. Two times minus four or eight minus two times 2 96.3 And that equals minus 14 08 16 killed. Jules. Now, the next part of the question is wanting you to compare the values of don't a genius. You got this way and from the way you got in 62. So I'm not gonna do it for all of them. But for the, um, 1st 1 report A When you calculate empathy and entropy information and then find it, you get 68.5 vs this 69 coach ALS that we got previously using our method, and so you can see these are very close, so above methods are pretty accurate when you're in reliable in comparison to each other when you're at standard temperature. If you want to calculate and see how Delta Jeannot changes at varying temperatures, you have to do the way they met. Mention mentioned on Problem 62 because that way you can account for the temperature factor better because you have to calculate Delta H and up the S using the table. But then T is allowed to vary so you can figure out how the temperature bearing will affect this value. And so that's the one you need to use when you're comparing temperature change for understanding conditions.