Calculate the percent composition of the following:
So how do we find the percent compositions of each element inside of potassium permanganate we’ve come to the right place my friend first we’ve got to find the total mass and then we can find those percentages watch how easy peasy this is bam so the first thing we’re going to do is write the elements we see in the compound so we have potassium we write that a little
Bigger potassium we have manganese and we have oxygen then we’re going to identify the number of atoms of each and that’s where the subscripts come into play now if you don’t see a subscript at the bottom of the element assume that there is a one there well because there is right so there’s one atom of each potassium and manganese and then there are four oxygens
Because the subscript of oxygen is a four then we’re simply going to take those number of atoms and multiply by the mass of the element and that’s where the periodic table comes into play so the potassium’s mass is going to be 39.10 magnesius is 54.94 and oxygen is going to be 16. so let’s write them on on so this is going to be 39.10 this was 54.94 and this was
16. then all we’re simply going to do is multiply this row on together so that we find the total mass of the element in the compound so this would be 39 so the total mass of potassium that is is going to be 39.10 total mass of machines is going to be 54.94 then the total mass of oxygen is going to be well not 16 because you got to multiply by 4 careful there
64. right and then to find the total mass of the entire compound just simply add this column on up and that works out to be 158 and there it is right that was the first step of the process finding the total mass of the compound now what i’m going to do is i’m going to add a column to this table to help us find those percents easy peasy from here bam so to find the
Mass percent of potassium we’re going to take the total mass of the potassium that’s why we calculated this row so it’s going to be 39.10 divided then by the total mass of the entire compound or 158.04 don’t worry about the units because the units will cancel but then you’ve got to multiply by 100 because we need it in terms of eight percent part over whole times
100 that is a percent calculation so this works out to be 24.74 percent all right that’s all there is to that one next for macanese it’s going to be the same thing take the total amount of magnese 54.94 and then divide it by the total mass of the compound uh 158.04 times that by 100 and we find the total percent here is going to be 34. make that a little neater
34.76 percent all right and then last but what the heck and then last but not least yeah there you go i’ll take the total mass of that auction 64. don’t worry about the zeros all right it might affect the significant figure account but you know quite honestly you know how i feel about that who cares about sig figs right 40.50 might say well my teacher will care
When he or she takes off you know 72 points and you’re starting out of the gate uh you know with a 28. so if you add these percentages together just to check yourself it should be 100 and that’s what i want for you on your next test all right and what we’ve done to help you out is we’ve created thousands upon thousands of videos for you in different subjects not
Only in chemistry here but we got mathematics we got physics we’ve got organic chemistry we’ve got a whole bunch of other stuff coming out all right so check out our channel and we’d love to help you get to where you need to go take care
Transcribed from video
How to find the percent composition of KMnO4 (Potassium Permanganate) By The Glaser Tutoring Company
