Ethanol 1C2H5OH2 is blended with gasoline as an automobile
fuel. ...

Question

Ethanol 1C2H5OH2 is blended with gasoline as an automobile
fuel. 
(c) Calculate the heat produced per liter of ethanol by combustion
of ethanol under constant pressure. Ethanol has a
density of 0.789 g>mL.

Accepted Answer

Hi everyone. This problem reads One Beauty is a very competitive renewable biofuel for use an internal combustion engines given its many advantages as it yields more energy is less volatile and doesn't cause damage to the engine, calculate the heat produced per leader of one beautiful combusted under constant pressure. If one button all has a density of 10.81 g per milliliter. So our goal here is to calculate the heat produced per one leader of one Butin all Okay. And we know that we have a combustion reaction. So what that means is our one button all is going to react with oxygen and it's going to produce products. Okay. And so our balanced equation for that is going to be the following. Okay, so now that we have our balanced equation in order for us to calculate the heat produced, we're going to want to calculate the standard entropy of formation but we're going to need to know the standard heats of formation for everything involved in our reaction. In order to get that value. Now the standard heats of formation are values that we can look up. So we'll go ahead and write out our standard heats of formation for everything in our reaction, we'll go ahead and start off with our first reaction. Okay, are one Butin all when we look up this value, the standard heat of formation is going to be negative. 327.10 kila jules our second reactant. Its in its standard state. So this is oxygen gas. Okay. Anything in its standard state is going to be zero. Okay, next, we have our first product, which is carbon dioxide. The standard heat of formation of carbon dioxide is negative 393.5 kg jewels. And lastly, we have our standard heat of formation Of H20. Okay, and this is gas. So make sure we're paying attention to what state it's in because the values are going to be different. So for H 20 is going to be negative. 241.8 to kill a jules. Now, for us to solve for the standard of our reaction, it's going to be the sum of our products minus the sum of our reactant since. So we're going to take the number of moles and for each product or reactant and multiply it by its standard heat of formation. But we're going to take the some of the products and subtracted from the sum of our reactant. And so this is what that's going to look like here. Okay, so the some of our products will start off with our products, we have eight moles of carbon dioxide. We're going to multiply that by its standard heat of formation, which is negative 393. kg joules. Plus our second product is H 20. Gas. We have 10 moles of that. So we're going to multiply it by its standard heat of formation, which is negative 241.8 to kill a jules. So that's the sum of our products and we're going to subtract it by the sum of our reactant. So our first reaction is that one? Beautiful. And we have two moles of it. So we're going to take two and multiply it by our standard heat of formation for one Butin all which is negative 327.10 kg jewels plus. We have 13 moles of oxygen gas. But we said that it's in its standard state. So this is just going to be zero. Okay, so we get a standard entropy change for our reaction equal to negative 4912 killer jules. Okay, so this is not our final answer because we need to calculate the heat produced per leader. Okay. And so we know that this is the this is the heat produced per two moles of one button All. See looking at our reaction up here, we have two moles of one beauty. And also this heat is per that two moles. So let's go ahead and write that out. Okay, so we have 4912 kg jewels per two moles Of one View and All. And our goal here is to calculate per one leader the heat produced per leader. Alright, so the first thing that we're going to want to do is go from, we're going to want to go from this two moles of you and all. Okay, so we're gonna take our our molar mass of one and all to calculate that. So in one mole Of one. Butin all going to our periodic table. We have Its molar mass is 74.14 g of one. Butin all Okay so we want to make sure our units cancel here and we can see here that are moles cancel. And so now we have killer joules per gram. But we want killer jewels. We just want killer jules. Okay so let's keep going. And we were given the density in this problem. So here's where the density comes into play. Okay we know that There is 0.81 g per one million liter. Okay so we can use that conversion to get rid of our grams. So now we have killer joules per Mill leader but we want per leader. So that means our last thing that we need to go is go from middle leader to leader. Okay so that conversion is in one leader there is 1000 male leaders. So our unit of male leaders cancel. And we're left with killer joules per leader. Okay so now we have what we want the units and we can do the calculation and when we do the calculation we get 2.7 times 10 to the fourth. Kill a jewel per leader which is what the problem asked for it. Wanted us to calculate the heat produced per leader of one. Butin all combusted so this is going to be our final answer. Okay, that's it for this problem. I hope this was helpful.

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