Number of moles of polymer formed

[Janiceleong26]

• Homework Statement

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?

 

[Borek]

Imagine you have two A. Can you make two pairs (AA) of the two A you have?

 

[insightful]

Choose a molecular weight for the monomer (say 100 g/mol) and play with the numbers.

 

[Janiceleong26]

Imagine you have two A. Can you make two pairs (AA) of the two A you have?

No..

 

[Borek]

No..

Do you see how it is related to the problem? And to the 1^st answer?

 

[Chestermiller]

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?

 

[Janiceleong26]

Do you see how it is related to the problem? And to the 1^st 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?

 

[Janiceleong26]

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) ?

 

[Borek]

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?

 

[Janiceleong26]

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?

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) ?

 

[Borek]

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.

 

[Janiceleong26]

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)

 

[Borek]

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?

 

[Janiceleong26]

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

 

[Borek]

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?

 

[Janiceleong26]

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?

 

[Borek]

Reread what I wrote, the answer is there. Start with the word "everything".

 

[Janiceleong26]

Reread what I wrote, the answer is there. Start with the word "everything".

OHHH... I see I see
Between 0.5 mole to 1/(6.02x10^23) mole , 10^-6 is within the range
Thanks !

 

[epenguin]

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?

 

[insightful]

...if it were extended in a line now far would a mole go...

Might it be on the order of light-days?

 

[Borek]

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.

 

[Borek]

Might it be on the order of light-days?

Don't guess, this is trivial to estimate.

 

[insightful]

Don't guess, this is trivial to estimate.

That wasn't a guess.

 

[epenguin]

I hoped Januce could discover and surprise herself.
And pick up a useful habit.

 

[Janiceleong26]

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?

 

[epenguin]

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.)