Question 10 homework

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Lucy Weaver 1K
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Question 10 homework

Postby Lucy Weaver 1K » Sat Oct 10, 2020 6:20 pm

I am a little confused about how to balance the reaction for the last question on the homework, it does not seem to be working out

Right now I have the chemical equation as
C4H8O +C3H7Br +Mg --> C7H16O

It doesn't seem to me that this equation is able to be balanced

Brennan McGurrr 3C
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Re: Question 10 homework

Postby Brennan McGurrr 3C » Sat Oct 10, 2020 6:29 pm

This confused me too. What I realized is that the carbons are balanced, which led me to believe there is a 1:1 molar ratio between 2-butanone and 3-methyl-3-hexanol. Other than the molar masses, that is all the information you need to do the stoichiometry, but I am definitely going to ask about it in my discussion section or office hours.

Benjamin Chen 1H
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Re: Question 10 homework

Postby Benjamin Chen 1H » Sat Oct 10, 2020 6:30 pm

I understand the equation doesn't seem to make sense since we can't see a Br or Mg species on the products side, but my section's TA said that the equation is balanced. There's probably more to this reaction than what is given (ie this reaction may be a multi-step reaction), so don't worry about balancing this equation. Also, this is an Organic Chem reaction and we don't really know how to look at these reactions yet.
I hope this helps.

Jason Nguyen_1B
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Re: Question 10 homework

Postby Jason Nguyen_1B » Sat Oct 10, 2020 7:05 pm

For this question, do we need to know the chemical formula 2-butanone and 3-methyl-3-hexanol in order to solve this question? And if we did, would we just search up what the chemical formula is if we didn't know beforehand?

Rachel Kho Disc 2G
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Re: Question 10 homework

Postby Rachel Kho Disc 2G » Sat Oct 10, 2020 7:39 pm

Jason Nguyen_1B wrote:For this question, do we need to know the chemical formula 2-butanone and 3-methyl-3-hexanol in order to solve this question? And if we did, would we just search up what the chemical formula is if we didn't know beforehand?


You would only need to know the formula so that you could figure out the molar masses, which you need to be able to do the stoichiometry. Hopefully if this appears on a test then they'll give us the molar mass, but if not you'll need to figure out the number of each atom. This is an organic chemistry problem which is kind of confusing, but when you look at how the molecules are drawn out imagine that there is a carbon atom attached to each kink in the molecule. Each carbon atom has to have 4 bonds, and it's implied that the carbon would be attached to a hydrogen which must have 1 bond. So in 2-butanone, there are 4 little kinks which means there are 4 carbons, and you attach as many hydrogens as you need so that each carbon has 4 bonds (note the double-bonded oxygen is already attached to a carbon that has two bonds, so you wouldn't need to add any hydrogens to that carbon atom because it already has 4 bonds). The end result should be C4H8O, and then you can calculate that molar mass. If my explanation is a little confusing, you can also google an image of the molecule!

At the end of the day, the molar mass for 2-butanone is 72.11 g/mol and the molar mass for 3-methyl-3-hexanol is 116.2 g/mol. But it's good to practice figuring out the chemical formulas in case it comes up on the spot and you don't have access to google to look it up!

Jason Nguyen_1B
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Joined: Wed Sep 30, 2020 9:34 pm

Re: Question 10 homework

Postby Jason Nguyen_1B » Sat Oct 10, 2020 8:14 pm

Oh jeez, I didn't know the diagram could be read like that to figure out the number of each atom. I understood your explanation pretty well but hopefully they give me the molar mass because the entire procedure seems a bit complex to me right now.

Joshua Swift
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Re: Question 10 homework

Postby Joshua Swift » Sat Oct 10, 2020 8:22 pm

I am quite confused on this question as well. The rest were all straight forward however this one I found myself having to look up additional information just to get the answers wrong still. I am using the same numbers as Rachel mentioned but ended up at incorrect answers nonetheless. Not really sure if I am messing something up but I flew through the rest with no problem.

Ralph Zhang 2L
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Joined: Wed Sep 30, 2020 9:55 pm

Re: Question 10 homework

Postby Ralph Zhang 2L » Sat Oct 10, 2020 8:29 pm

Joshua Swift wrote:I am quite confused on this question as well. The rest were all straight forward however this one I found myself having to look up additional information just to get the answers wrong still. I am using the same numbers as Rachel mentioned but ended up at incorrect answers nonetheless. Not really sure if I am messing something up but I flew through the rest with no problem.

For this question I just looked at 2-butanone and 3-methyl-3-hexanol (which are 1:1 in ratio) and ignored everything else. Once you calculate how many moles of 2-butanone that was used in the experiment the whole question can be solved.

Ayesha Aslam-Mir 3C
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Re: Question 10 homework

Postby Ayesha Aslam-Mir 3C » Sat Oct 10, 2020 8:54 pm

Hi, trying to understand how the strucure creates the molecular mass, I'm thinking each vertex represents one carbon plus an additional hydrogen if not already bonded to another distinct molecule? So using this information, could add the mass of carbon and hydrogen for each vertex since the carbons seem to have full shells, plus the mass of the other distinct atoms (like oxygen) that are shown to be bonded at some carbon on the chain. Would this strategy work to find the mass?

Rachel Kho Disc 2G
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Joined: Wed Sep 30, 2020 9:46 pm

Re: Question 10 homework

Postby Rachel Kho Disc 2G » Sun Oct 11, 2020 2:56 pm

Ayesha Aslam-Mir 2E wrote:Hi, trying to understand how the strucure creates the molecular mass, I'm thinking each vertex represents one carbon plus an additional hydrogen if not already bonded to another distinct molecule? So using this information, could add the mass of carbon and hydrogen for each vertex since the carbons seem to have full shells, plus the mass of the other distinct atoms (like oxygen) that are shown to be bonded at some carbon on the chain. Would this strategy work to find the mass?


Ahhh yeah I'm realizing my explanation may not have made perfect sense in the moment, but basically you want to be able to fulfill the 4-bond rule for carbon. At each end of the molecule, carbon is only bonded to one other carbon so you have to add 3 hydrogens to make 4 bonds. You wouldn't need to add anything to the carbon attached to the oxygen, because it already fulfills the 4-bond rule (two bonds to the oxygen and two bonds on each side to other carbons). To the carbon in the middle that is only attached to 2 other carbon atoms, you would need to add 2 hydrogens to make 4 bonds. Again, this is a technique that comes with practice and it's more of an organic chemistry concept that probably won't come up often in this class.


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