A reactiont akes place at a constant pressure of 1.10 atm with an internal energy change (ΔE) of 71.5 kJ and a volume decrease of 13.6 L. What is the enthalpy change (ΔH) for the reaction? (1 L-atm = 101.325 J)

Video transcript

Hi everyone this problem reads a reaction takes place which resulted in an internal energy change of positive 68.4 kg jewels and a decrease in volume of 11.5 liters. If the reaction takes place at constant pressure of 1. atmospheres calculate the entropy change for The reaction and we're told one leader atmosphere is equal to 101. jewels. So the question that we want to answer for this problem is the entropy change. And so we want to calculate the entropy change for the reaction. Okay. And a key piece of information we're told is that this really Action is taking place at constant pressure. Alright so the equation that we're going to want to use to solve this problem is internal energy change is equal to heat plus work. Okay so let's go ahead and write down what's given in the problem in the problem we're given the pressure. We're told the pressure is 1. atmospheres and were also given the internal energy change. So the internal energy change is positive 68.4 kg jewels. And we're also told the change and volume, the change in volume, we're told there's a decrease in volume. So that means we have minus 11.5 liters. Okay so going back to our equation that we wrote out the key piece of information says constant pressure. Okay, so at constant external pressure heat is going to equal entropy change. Alright so this is at constant pressure. And so what we can do now is we can rewrite this equation to substitute our our entropy change for heat. So we're going to get internal energy change is equal to heat which we're going to replace with entropy change plus work. Alright. And another thing that we can know is work is equal to negative pressure times volume change. So we can go ahead and replace work as well in our equation. So what we're going to get when we replace both our heat and work variables is internal energy change is equal to entropy change minus pressure times change and volume. Okay and the question is asking us to calculate the entropy change for the reaction. So what we want to calculate here is this delta H which is our entropy change. So let's go ahead and isolate that variable when we isolate this variable. We're going to bring it. We're going to have it on one side on its own. So what we're going to get is and entropy change is equal to internal energy change plus pressure times change in volume. Okay so what we did was we brought this pressure times change in volume over to the left side which makes it positive now. Okay so now We can go ahead and plug in what we know based off of what was given in the problem so our our entropy change is going to equal our change in internal energy which the value that was given is positive 68.4 kg jewels plus pressure were given the pressure. It's 1.22 atmospheres and we were given the volume change which is negative 11.5 liters. Alright, so let's go ahead and simplify this. So we're going to get positive 68.4 kg jewels plus When we take 1. atmospheres and multiply it by the volume change, we get negative 14. leaders atmosphere. Alright, so we want this leaders atmosphere and kill a jules. Okay, so we want to convert this from Leaders Atmosphere to kill a jules because our entropy change needs to be in kilo jewels and we can convert this Leaders atmosphere to kill a jewels using what we Was given in the problem. And the problem we're told one leader atmosphere is equal 101.3-5 jewels. So let's go ahead and use that to convert our leaders atmosphere too. Killer jewels. Because we want to make it match This unit here. Alright, so let's go ahead and do that. So we have 14.03 leaders atmosphere. All right. And we want to go from leaders atmosphere to Jules. So let's use what was given in the problem. And the problem we're told one leader atmosphere Is equal 101.3- jewels. Okay, so now our units of leaders atmosphere cancel. And we're left with unit of jewels. Now we want to go from jewels to kill a jewels and one kill a jewel. There is 1000 jewels. Our units for jules cancel. And now we have the units of killer jewels. So let's do this calculation we're going to take 14.3 and multiply it by one oh 1.3 to 5 and then divide by 1000. When we do that we're going to get negative because we had a negative here. Okay, so we'll keep that negative there. So we have negative 1. kila jewels. All right, so this 1.42 kg jewels will go ahead and plug that in there. Okay, so what we're going to get is our entropy change is equal to positive 68.4 kill a jules -1.4 to kill a jules. Okay and when we do this calculation we're going to get positive 67 kg jewels. Okay so our final answer will write it down here are entropy change for This reaction is equal to positive kg jewels. And this is going to be the final answer. That is it for this problem? I hope this was helpful