 All right, I'm going to do percent and yield yes another test of today, and it's a little late, but At least it'll be up here for quarter exam Let's say your chemistry teacher is one of those crazy ones that expect you to do stoichiometry. Oh And you do problems like say that one That's from your study guide this three-step problem We had to go from grams of oxygen to grams of water using the the synthesis equation So you've done all this fantastic wonderful work, and now the question is what next? This number that you get at the end is what we can call theoretical yield It's what would happen in a perfect world if there were no loss of energy in the system if Everything was perfect you measured out all your reactants perfectly and everything that's what you're supposed to get 141 grams of water But as we all know full well, we don't live in a perfect world, and so you never see that you never get something That's perfect and pretty much anything. There'll be in what we call an actual yield So theoretical There we go theoretical yield What you would hope to get what you predict an actual yield is what you would actually get in your Real experiment if you actually ran that reaction and measured how much product you you made So let's say we run this experiment And I am just going to make up a number here I'm not actually going to get out hydrogen and oxygen and do the experiment I'm just going to make up a number here Let's say we actually do this experiment with 125 grams of oxygen, and in the end we get 122 grams Again according to our math our theoretical should be 141 We need a way of indicating how good our reaction was or how good we were at running the reaction And we do that the same way you do in all your classes We want to see how you well you did your class how well you learned your material We calculate a percent and we put it on your report cards every quarter And we do the same thing here if we wanted to see how well we did our reaction here How well our yield actually held up against the theoretical we would calculate a percent and it's called percent yield It is actual Divided by theoretical times 100 It's the same way you calculate any percent a percent is a part divided by the whole Times 100 so if you wanted to figure out your percent on a test Your part would be the number you got correct The whole would be the number of questions Times 100 Again part the number you got right Divided by whole the total number of questions times 100. This is the same thing. This is the same equation This would be our whole we shouldn't get more than that Yeah, in school sometimes you get a hundred and five percent on tests with bonuses and stuff like that But in real world there is nothing more than a hundred percent You can't get more than a hundred percent So the theoretical this number here is the whole that's the max That's the total that you can get This number is a part of that So when we look at the percent yield equation, it's no different than this one part divided by whole times 100 Part divided by whole times 100 So we do our calculation here the percent yield is going to be equal to 122 over 141 times 100 Now these things are the same unit and they have to be the same unit so they'll cancel because there's no unit on a percent 122 divided by 141 is point eight six five two four eight two two seven times 100 Is eighty six point five two four? I'm just gonna round that to a whole number because that's what I'd like to do Percent yield is eighty seven percent So we can see here that that's not too bad a percent yield this were a class That would be a very solid B Not too bad Of course, it could be better. We could have 90 something percent yield We could be a whole heck of a lot worse, and we could have 30 40 percent yield Hopefully you're great on the stoichiometry test is something closer to that and 40 or 30 or something lower Good luck with that