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Video Solution: Alkanes spontaneously burst into flame in the presence of el...

Problem

Alkanes spontaneously burst into flame in the presence of elemental fluorine. The reaction that takes place between pentane and F2 gives CF4 and HF as the only products.  

(a) Write a balanced equation for this reaction. 

Video Transcript

Hey everyone. So in this question we're going to be writing on a balanced equation, okay? So I know you probably thought you were done with these days, but all we need to do now is we're going to be given a hydrocarbon with the name pentane and we know we can convert that to a molecular formula and it's simply balance out atom for atoms, okay? So this shouldn't be too bad it's just testing us now on our knowledge to come up with a molecular formula for pentane? Well, pentane is just going to be five carbons. So, 1, 2, 3, 4 and 5. Now, we know that is going to be C5, instance it's a regular alkane, we expect it to follow the formula CnH2n plus 2. So, how many hydrogens do you expect 12, right? We expect this to be H12, so let's just write now our link up here, so I'll balance out first which atom do you want to do, right? Well start with carbon, right? So we see five carbons on one side what we need to do is simply take that five and fill it in over here, okay? So we're going to be balancing out carbon, hydrogen and fluorine. So, right now we just say, how many carbons do we have here? five. What about on the other side, well, we have five. So, those are good. Now, we need to start balancing out our hydrogens and our fluorine, so let's look at our hydrogens, we see we have 12 on the left and what we do is if we take that number 12 and place it over here to the right, okay? So, so far now we have 12 hydrogens, 12 hydrogens, and all that's left the bounce out is which atom? our fluorine. So here, let's take a look, we need to do actually some help because we have 5 to the F that has 4 n 12 to the F that just is 1, so this number we expect to be 12 because 12 times 1, over here is going to be five times 4 for chlorine, so we expect actually 20, right? So we need to add up 20 plus 12, we're going to get to 32. So, how do we turn this in 32? we simply add 16, okay? And 16 times 2 will be 32, so now it looks like we have all of our atoms balance, this is going to be a 32, we can circle that, circle this and circle that, okay? So, our numbers here, this will just be a 1 will have 16, 20, or excuse me, 5 here and 12, okay? So these are going to be the numbers that balance out our complete equation that was given to us. Alright, so I hope this makes sense, let me know if you have any questions.

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