How Many Moles of Polymer Are Formed?

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SUMMARY

The discussion centers on calculating the number of moles of polymer formed from monomers in a chemical reaction, specifically the reaction 2A → AA. Participants clarify that to form one polymer molecule, at least two monomers are required, leading to the conclusion that starting with 1 mole of A results in 0.5 moles of AA polymer. The conversation also touches on the theoretical implications of molecular weight and the vast lengths of macromolecules, such as DNA, when considering 1 mole of such substances.

PREREQUISITES
  • Understanding of basic mole concepts, including Avogadro's number (6.02 x 10^23).
  • Knowledge of polymer chemistry, specifically the reaction mechanisms of monomers.
  • Familiarity with molecular weight calculations, particularly for common monomers.
  • Basic comprehension of macromolecules, including DNA structure and length calculations.
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  • Study the concept of Avogadro's number and its applications in chemistry.
  • Explore polymerization reactions and their stoichiometric implications.
  • Investigate molecular weight calculations for various monomers and polymers.
  • Research the physical properties and lengths of macromolecules, particularly DNA.
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Chemistry students, polymer scientists, educators in chemical education, and anyone interested in the quantitative aspects of polymer formation and molecular calculations.

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  • Homework Statement

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2. The attempt at a solution
I chose no. 1 only, but the answer is 2&3, I can't seem to see how 10^-6 came about. And for C, I'm not clear how it came about too.. Is it because 1 mole consists of 6x10^23 atoms, so no. of moles of the polymer is 1/(6x10^23) ? And why is 1 mole wrong?
 
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Imagine you have two A. Can you make two pairs (AA) of the two A you have?
 
Choose a molecular weight for the monomer (say 100 g/mol) and play with the numbers.
 
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Borek said:
Imagine you have two A. Can you make two pairs (AA) of the two A you have?
No..
 
Janiceleong26 said:
No..

Do you see how it is related to the problem? And to the 1st answer?
 
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What would happen if the all the monomer reacted with itself to form one long gigantic molecule of enormous molecular weight. How many moles does 1 molecule represent?
 
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Borek said:
Do you see how it is related to the problem? And to the 1st answer?
Erm.. Is it like for one polymer to form, we need at least two monomers? So it should be at least two moles till infinite? What about option 2?
 
Chestermiller said:
What would happen if the all the monomer reacted with itself to form one long gigantic molecule of enormous molecular weight. How many moles does 1 molecule represent?
Erm, 1/ (no. of monomers joined) ?
 
Janiceleong26 said:
Erm.. Is it like for one polymer to form, we need at least two monomers?

So, how many moles of the product you will get?

Now try to answer Chester's question. Basically he is asking - 1 molecule, how many moles is it?
 
  • #10
Borek said:
So, how many moles of the product you will get?

Now try to answer Chester's question. Basically he is asking - 1 molecule, how many moles is it?
Chestermiller said:
What would happen if the all the monomer reacted with itself to form one long gigantic molecule of enormous molecular weight. How many moles does 1 molecule represent?
I'm not sure.. 1/(no. of moles of monomers) ?
 
  • #11
1 molecule of anything - how many moles of that substance? Don't think about monomers and polymers for a while, this is a simple, basic question about moles as such.
 
  • #12
Borek said:
1 molecule of anything - how many moles of that substance? Don't think about monomers and polymers for a while, this is a simple, basic question about moles as such.
1/(6.02x10^23)
 
  • #13
OK, so, if everything reacted, you will get a single polymer molecule, or 1/6.02×1023 moles of product, yes?

Now, if the reaction were exactly 2A→AA, and you started with 1 mole of A, how many moles of the AA polymer would be produced?
 
  • #14
Borek said:
OK, so, if everything reacted, you will get a single polymer molecule, or 1/6.02×1023 moles of product, yes?

Now, if the reaction were exactly 2A→AA, and you started with 1 mole of A, how many moles of the AA polymer would be produced?

1/2 mole of AA
 
  • #15
So, if there was a simplest reaction, there is no way 1 mole of polymer could be produced, right? But depending on the product everything between 1/2 mole of 1/6.02×1023 is possible, isn't it?
 
  • #16
Borek said:
So, if there was a simplest reaction, there is no way 1 mole of polymer could be produced, right? But depending on the product everything between 1/2 mole of 1/6.02×1023 is possible, isn't it?
Yup true. Thanks for the help
But what about option2? :biggrin:
 
  • #17
Reread what I wrote, the answer is there. Start with the word "everything".
 
  • #18
Borek said:
Reread what I wrote, the answer is there. Start with the word "everything".
OHHH... I see I see :woot:
Between 0.5 mole to 1/(6.02x10^23) mole , 10^-6 is within the range
Thanks !
 
  • #19
OK 2 and 3 are both correct answers. But I think this is a case of "when you've got the answer it's not finished."
2 is a typical possible figure I think for a polymer.
For 3 I think the operative word in the question is theoretically.

Would you care to work out how long is 1 mole if it's one molecule?
I think macromolecules don't come longer than DNA. One fairly avverage human chromosome has 220X106 base pairs in a DNA molecule thought to be continuous. In the ordinary double-helical structure contains about 10 basepairs per turn and each turn is about 0.34 nm long. It normally folds back on itself, but if it were extended in a line now far would a mole go, would you care to work out and tell us?
 
Last edited:
  • #20
epenguin said:
...if it were extended in a line now far would a mole go...
Might it be on the order of light-days?
 
  • #21
Hm, question never said polymer can't undergo crosslinking. I have no problems assuming a huge object made of a crosslinked polymer is actually a single molecule.
 
  • #22
insightful said:
Might it be on the order of light-days?

Don't guess, this is trivial to estimate.
 
  • #23
Borek said:
Don't guess, this is trivial to estimate.
That wasn't a guess.
 
  • #24
I hoped Januce could discover and surprise herself. :oldsmile:
And pick up a useful habit.
 
  • #25
epenguin said:
OK 2 and 3 are both correct answers. But I think this is a case of "when you've got the answer it's not finished."
2 is a typical possible figure I think for a polymer.
For 3 I think the operative word in the question is theoretically.

Would you care to work out how long is 1 mole if it's one molecule?
I think macromolecules don't come longer than DNA. One fairly avverage human chromosome has 220X106 base pairs in a DNA molecule thought to be continuous. In the ordinary double-helical structure contains about 10 basepairs per turn and each turn is about 0.34 nm long. It normally folds back on itself, but if it were extended in a line now far would a mole go, would you care to work out and tell us?
Sorry for the really late reply as i was busy with exams.

I'm not too sure if my working is right.. but this is what I did:

1 basepair has a length of 0.034nm
1 molecule of DNA has 220x10^6 base pairs, in 1 mol there would be 220x10^6 x 6.02 x10^23 =1.324 x 10^32 base pairs.
Length of 1 mol of DNA would be 1.324 x 10^32 x 0.034 nm = 4.50 x 10^21 m

I'm sorry, I am not too sure what you mean by how long is 1 mole if it's 1 molecule.. I thought 1 mole has 6.02 x 10^23 molecules?
 
  • #26
That is truly astrononomical. What I had actually meant was one mole of nucleotide or of basepairs.

When I worked that out (a single human chromosome unwound if it could be straightened but still the double-helical structure) this was already fairly astronomical, a large fraction of a light year. 1mole of DNA as you have calculated is a large mass and a huger length of zillions of light years.

The single human chromosome unwound if it could be straightened in this way is reckoned to be a few centimeters. The chromosome you see photos of in your genetics texts is of order, if I remember, a micron. Very condensed. (Though remember those pictures where they are seen and counted etc. are in a cell-cycle phase where they are most highly condensed.)
 

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