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### The following is known as the thermite reaction: …

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Manhattan College

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Problem 70

Write balanced equations that describe the formation of the following compounds from elements in their standard states, and then look up the standard enthalpy of formation for each substance in Appendix C: (a) $\mathrm{H}_{2} \mathrm{O}_{2}(g),(\mathbf{b}) \mathrm{CaCO}_{3}(s)$
(c) $\mathrm{POCl}_{3}(l),(\mathbf{d}) \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l) .$

Answer
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## Video Transcript

guys, We're going to be doing problem number seventy in chapter five of Chemistry Central Science. So we're going to be looking at these four compounds right here. A hundred peroxide counts. Calcium carbonate Pio OOCL three e and C to H five o. H. We're going to write the balanced equation for the formation of these of these compounds, and then we're going to look look up the Delta H Value. So let's sort of hydrogen peroxide. So there's gonna be a tch too, plus O two yield age too. Oh, two. So we have two ages on left. Two inches on the right, too. Who owes unless to those on the right. So that means our equations balance. And if you look at Appendix C, you confined the delta H of formation of these compounds, and that is going to be negative. One. Thirty six x point one and zero killer jewels from killing Jules. Now, let's locate calcium carbonate. So we're gonna add calcium. We're gonna and our we're going to add our carbon. And now we're gonna add the oxygen. No, this will produce our carbonate. Now let's see what we have here. We have one counts on the left. One calc, one calcium on the right when carbon left when carbon on the right. And we have two options, like a three on the right. So remember, we're talking about thie. Standard heard entropy information were actually producing one mole of our product. So were you? No. So we have to create a scenario. We're only using one mole of calcium carbonate. So? So we can. So instead of having a hey ah, define an indigent coefficient, we're going to be using a fraction. So we're going to using three half of oxygen Jin, So oh, you break up to two and half and half. You have individual auction, Adam. You must buy that by three. That gives you three auction. Which bees? For carbon E. Now we're going to go to P o OOCL three. Yeah, three. Before we do that, let me just write down the standard dental pia formation for casting carbonate twelve seven point one. Killer Jules, feel to gas deals. P Oh, see, l three liquid liquid. So we have won five years in the left. One on the right. One auction on left. I started to action, then left one on the right. So we have to make this one half and we have to. Chlorine Zon left three on the right. So we're gonna make this into three halfs and the we got Appendix C. We can see that Delta H permission for POC l three is minus five. I have ninety seven point zero killer Jules. Also be very aware. Hear that? That the standard and the information depends on the phase. So So you may find some samples that are books you can find the information for the liquid phase and also the solid phase. But remember, these are two very different things. And now we're going to look at sea to eighty five o h. So we're gonna have carbon plus hydrogen. Yes. And remember when were talking about the formation of a compound? Where were you talking about formation from its individual. The individual elements in their standard states and the individual element had to be for mission individual met. Their Shan state is always going to be zero. Kill it, Jules. Girls. So oxygen. The delta of action is going to be zero. However, the delta age of lets an individual option and that is not going to be zero. Similarly, be thie Delta H of solid calcium. That's going to be zero. But let's a liquid calc him. That's not going to be zero. So No. So here we have here we have one on one carbon and left two on the right. So we added two in front of here. Two options on the left, five on the right amount of five over two. Oh, I'm just not. We have five and six, so we're gonna So we're going to add eight three here. We owe to which we have two on the left, one on the right. So we're gonna have one half and the delta age for ethanol. Oh, that is negative to seventy seven point seven killer Jules else. And that's how you solve these kind of problems. Do you remember when you were creating in Bangor molecule? We're creating it from its Adams in their standard state. And when us and we all said to remember to look up the correct at the H values which you confined Appendix C, but also be wary of the phase you're using because that is one to affect their delta. The values that you're