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Problem 51

20.51 Calculate $\Delta G^{\circ}$ for each reaction using $\Delta G_{\mathrm{f}}^{\circ}$ values:

(a) $2 \mathrm{Mg}(s)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{MgO}(s)$

(b) $2 \mathrm{CH}_{3} \mathrm{OH}(g)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)+4 \mathrm{H}_{2} \mathrm{O}(g)$

(c) $\mathrm{BaO}(s)+\mathrm{CO}_{2}(g) \longrightarrow 2 \mathrm{aCO}_{3}(s)$

Answer

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## Discussion

## Video Transcript

It's just the question that spit tedious but honestly is not conceptually very difficult once you have the idea down. So we have these two reactions and were asked to find the Delta G of the reaction. Um, and other Jeannot we spent specifically said to 98 Kelvin, I want a TAM And so the Delta G is going to be equal to the some of all of the Delta Jesu formation. All the products on this case is going to be times their coefficients. We have two times the Delta G formation of magnesium oxide minus all the Delta Jeez for the products and so would have minus two times the delta G of formation of magnesium plus Delta G of formation for +02 And so this is gonna be the basics for mouth everything. It's always products minus two jackets. You could remember that those words products, mice, practice. You'll have every question this. So before we go on, uh, so we're gonna you know, you can get all these Delta G information values on a table. We don't have to search for all of them, because if we remember, whenever we have an element in a standard state. It's Delta G information zero and so zero and zero because magnesium and auction here understanding saying so. We have to look at the Delta view of formation of NGO, and I did, and it's equal to 500 69.4. And so multiply that by two. Um, for me, I believe that's negative. Um, yeah, it's a negative. And then when you do that, you'll get that the overall values 1001 to 38 Killer jewels, Permal or just killer jewels. Uh, it's implied that its Permal, because it's a tell a story of formation. And so ah, that's that's the every for this reaction. So this reaction really has a density of negative 1138 till adjustable next one products minus reacted. So Delta G is gonna equal 1st 2 times the Delta G of CO two, um, which is negative 394 0.4 plus four times a Delta G of H +204 and H +20 which is negative. 228.6. Now we're gonna do with the reactions, but they're all gonna be minus. So we're gonna take a knife. So too, will ignore this in its standard state. And so we have minus to times the delta G of C H P O h, which is negative 1 61 And now you like you can perceive pretty obviously, you have to be careful with these. Ah, units that can easily, very easily get mixed up. But we'll end up with negative. 1379.4 killed. Jules, Her mom. Um, yeah, this really Like I said, it's not difficult. Conceptual. It's just tedious. And you have to be careful. That's what I'm working through It with us. Last one Delta G. Look up. Burying, uh, carbonate that values really, really negative. Negative. 1137.6. Now, these two, uh, product reactions there going minus, so minus. Now, Delta G of boko um is 5 25 negative 5 25 So those the nine years will cancel out and then we'll also have co two, which we had before is negative. Um, negative 3 94 So you see, we have the negative because it's a reactive plus the negative that comes nationally from itself, that you information any other way. We're gonna get end up getting a smaller negative number 2 24 killer jewels. Formal. She makes sense. We start with the big *** number and then add a couple of smaller pauses numbers.