Hess's Law and Cycles

be balanced, ok, these numbers have to be balanced, otherwise you know it could go wrong, same with combustion, it's also very important, okay, so let's continue with our little one is like we've done before. we have and you can see we have four lots of nh3, so for many nh3 there will be four times, nh3 is minus 46 for that man, okay, and that will be minus 1/8 hole, okay, and you can see here. nobody that flows, we don't actually have a value for flow or what we do, but it doesn't actually hold and like a number greater than 1 is zero, the reason why zero elements is because and are elements and that's literally everything by definition. you can't form an element from an element because you do something so that there is no entropy change there, that's really important because they might ask why our elements have to change from zero and that's because their elements, that's all, there is no another reason for it, you know you can't. form it and form an element, nothing happens, so let me leave that one and then we come to this side, so we are doing the formation of nf3, we only have nf3 olive warm, so that will be minus 1 1 4, so that is easy and then we're going to send 3 batches of ammonium fluoride, which is this one here, so we're going to add it three times by - and 4 6 7 okay, so member to multiply it by 3 and if adding that we should get minus 1 4 minus 1 401 and the servant council that one alpha and minus 1 1 4 and we add that to minus 1 401, let's underline them, these are the two numbers that we are going to add, so if we add both numbers and we have to total the change in enthalpy of formation for this side, since minus 1 5 over 5 goes well, so just like with the other one, we need to calculate the end that is going to be changed and for this reaction that is this value here, so it will put the little red question mark there , we need to work on that one, so again, whatever route we need to take, so we need to go from here to here, that's the value we're trying to solve. but we can't go this way, so we go up here with Amal there, okay, then we're going to go here and up here to get to the same place, so I'm pretty simple, it's a look, so I'm going to take out, so that's going to change that to a plus sign, so it's actually going to be one in four pretty simple and then we'll go down here, so we'll keep the same sign 184: one five one. five, okay, now if we put that into our calculator and we should get minus 1 3 3 1 and that's kilojoules per mole, very important, okay, and that's the answer that goes there again, try to start from anywhere in the cycle , remember the rule if I have with the we keep the equal sign against the time we change inside the number remains the same put it there go to the side keep it at 0 that is very important if not something went wrong you have to go back and check this, that is a very good way to check, okay, you can also do the linear equation, so let's do it quickly, so this will be Delta and our detail H, this is done reaction enthalpy now for this one. is the sum of formation put these products first minus the sum of the enthalpy of formation and this is a burnt product sorry these are reactants okay these are reactants so it doesn't become the cycle but notice again that is divided backwards, now its products less. reactants, if you are going to make the equation linear, so you don't have all the changes for your products yet, subtract it from all the changes that will be in your actions that will give you the reaction enthalpy and really very difficult openings.

Again, you can see how similar they are and you can't really afford to mix them up, so again

cycles

will probably work better for you in this case, but there we go, there's the HESA cycle and make sure you understand this. Well, you know, it's a very, very important area of ​​chemistry. Any questions regarding your slides, I'll simply put them in the message box below. I'll try to move around to try to answer any questions at that time. That's Hess, so it's not that bad, but yeah, that's it, bye.