Diazomethane is a highly poisonous, explosive compound because it readily evolves N2. Diazomethane has the following composition by mass: 28.57% C; 4.80% H; and 66.64% N. The molar mass of diazomethane is 42.04 g/mol. Find the molecular formula of diazomethane, draw its Lewis structure, and assign formal charges to each atom. Why is diazomethane not very stable? Explain.

Video transcript

Hello everyone today. We are being given the following problem and asked to solve for it, declare acetylene is an unstable liquid that explodes readily at its boiling point of 33 degrees Celsius. The mass percent composition of declare, oh, acetylene is 25.3% carbon and 74.7% chlorine with a molecular weight of 94.92 g per mole. We are then being asked to determine the molecular formula for this molecule and to draw reasonable lewis dot structure. We also need to assign formal charges to all of the atoms in the structure and explain why di chloral a ceiling is unstable. So the first thing that we want to do here is we want to get how many moles that we have of each adam For carbon for example, we're going to take the percentage that we have 25.3%. And we're going to actually Divide that by the molar mass of one carbon atom which is 12.01 according to the periodic table. And when we do that we receive 2.11, we're gonna do the same thing for chlorine for chlorine. Our percentage is 74.7%. And we're going to divide that by the molar mass of chlorine and according to the periodic table that is 35.45 g per mole. And when we do that we also get 2.11. The next thing we have to do is we then have to take both of these numbers that we just obtained and divide by the smallest one and fortunately there the same number. So they will each just be equal to one giving us a formula of C C. L. Or carbon chloride. So We have to take the molar mass of carbon and chloride which when we take the molar mass of carbon and add it to chlorine, we get a molar mass of 47 0. grams per mole. Now we have to calculate in and would be the number that we're going to use to multiply this empirical formula that we have the CCL and so to calculate in, We're going to take in and we're going to equal that to our molecular weight given to us in the question. So are 94.92 g per mole. We're going to divide that by the molecular Mueller mass that we just sold for for the empirical formula which is 47.46 g per mole. And then we do that, we receive a value of n equals two. And so we can take that too. We can multiply our empirical formula to get let's see we c c c L two and then we'll just add times two and we get an answer of c two Cl two or Carbon Chloride. Now we have to connect these atoms and draw our lewis structure. So typically with that we're going to follow the principle that the lower electro negativity results in a more centralized atom and therefore according to the periodic table carbon is more is less electro negative than chlorine. So it's going to be in the center And since we have to we are simply going to draw one carbon here connected to another carbon here we are then going to draw both chlorine to the right of that carbon and to the left of that carbon. And so now we have connected all four of these atoms using three bond lines. And so we can use the role that each bond line has two electrons. And so with this structure we have six electrons that we have used. So we've already used six electrons. If we want to calculate the total number of electrons, we simply take the amount of each atom that we have. So we have two carbons and multiply that By its valence electrons. And so according to the periodic table, carbon is in the fourth group. So it has four valence electrons and we have eight electrons from carbon for chlorine. We're gonna do two times chlorine, which chlorine is in the seventh group. So that will be two times seven valence electrons giving us there or a total of 22 electrons that we can use. And we've already used six of those. So now we have In our remaining 16 electrons that we can use. And so when it comes to drawing in the remaining bond lines and electrons we must first do a couple of things first, we have to complete the outer shell of each electron. So this chlorine on the right and on the left can hold a maximum of seven valence electrons due to being in the seventh group on the periodic table. And what we're gonna do, we're gonna draw seven, we're gonna draw six additional electrons around each chlorine atom to complete. It's complete. It's full octet of eight electrons. And so now that we have used 12 of these electrons, We have four remaining. And so now that we've taken care of the ox head for chlorine, we have to take care of the octet for carbon. And so what we're going to do is we're going to draw an additional two bond lines between those carbon atoms. Now each carbon has eight total electrons surrounding it and it has four valence electrons immediately attached to it. So this structure here would be our lewis dot structure for carbon chloride. And so now to calculate our formal charges, we're going to do that down here and we're going to see the formal charge is equal to the number of valence electrons that we have, minus how many bonding electrons we have minus how many non bonding electrons we have. So we're gonna use this formula to calculate a formal charge for chlorine first and then carbon. So for chlorine, the valence electrons is seven. The number of bonding electrons or the bonded lines that we see as one. And then the number of non bonding electrons or loan or electrons that we see surrounding it is six giving us a formal charge of zero. Now we do the same thing for carbon, carbon is in the fourth group and therefore has four valence electrons. It has Well both of these carbons actually have four bond lines attached to them or four bonding electrons. So we're gonna go ahead and put four and then it has zero loan pairs around it. So therefore it will have a formal charge of zero. So both of these atoms will have formal charges of zero. So the formal charge of chlorine is zero in the formal charge of carbon is zero. And so here comes the last part saying why declare a ceiling is unstable. So The bond between these two chlorine atoms, this triple bond here and I'll label it down here as part of question seven or part of the answer choice answer seven. This triple bond here. So we'll say this triple bond is electron rich. And so what do we know about electron rich species, electron rich species like to perform reactions, they're very reactionary. You have a lot of electron density within that triple bond. And so it easily want to so to speak, attack another substance known as a nuclear filic attack. And so this is related to its instability because if something has too much of one charge that built up of that charge is gonna make that molecule very unstable. It's going to want to react spontaneously. And so, due to this triple bond nature, that is why this declare, oh, a seedling is unstable. And now we have answered the complete question. I hope this helped, and until next time.