Mod 7 polymers (1 Viewer)

[NexusRich]

Please provide working out and explain how to do this question

 

[jimmysmith560]

This question was previously asked in a different thread. This was suggested:

There are two types of polymer processes. These are the equations we use for the calculations for both:

Addition polymerisation: n monomer --> polymer

Condensation polymerisation: n monomer --> polymer + (n-1) H2O

All you have to do is select the correct equation and then substitute molar masses in and change the --> to an equals sign.

Here it is a condensation polymerisation process because 4-hydroxybutanoic acid reacts through OH and COOH to eliminate water molecules.

It cannot be an addition polymerisation process because these require the monomer to contain a carbon double bond (C=C). For example, propene, ethene, chloroethene are all things that would undergo addition polymerisation since they have a C=C.


Applying this to the question:
n monomer --> polymer + (n-1) H2O
as it is condensation polymerisation

n = 1000
monomer = 1 + 16 + 3(12 + 2x1) + 12 + 2x16 + 1 = 104 g/mol

1000 x (104) = polymer + (1000-1) (2x1 + 16)
104000 = polymer + 17982
86018 = polymer
polymer = 8.6 x 10^4 g/mol (2 sig figs)

I hope this helps!

 

[tito981]

Please provide working out and explain how to do this question

If its from baulko 2019, the answer says D but it is the one as state by jimmy so C.

 

[NexusRich]

This question was previously asked in a different thread. This was suggested:



I hope this helps!

Thank you so much. Could you please explain why condensation polymers produce n-1 moles of water ? I have seen some sources say that they could produce 2n-1 moles of water so it got me confused.

 

[jimmysmith560]

Thank you so much. Could you please explain why condensation polymers produce n-1 moles of water ? I have seen some sources say that they could produce 2n-1 moles of water so it got me confused.

No worries. The above answer was originally provided by jazz519. It would be a good idea to ask him as I'm sure he will be able to answer this particular question directly.

 

[jazz519]

Thank you so much. Could you please explain why condensation polymers produce n-1 moles of water ? I have seen some sources say that they could produce 2n-1 moles of water so it got me confused.

2n -1 is usually what is used if you have 2 different monomers being added together.

So for example: n monomer 1 + n monomer 2 --> polymer + 2n-1 H2O

 

[CM_Tutor]

Thank you so much. Could you please explain why condensation polymers produce n-1 moles of water ? I have seen some sources say that they could produce 2n-1 moles of water so it got me confused.

If a condensation polymer is made from a single, bifunctional (having two different FGs), monomer - such as in the conversion of lactic acid to polylactic acid, or the conversion of glucose to cellulose or starch, then (n-1) water molecules are produced as a by-product:

n lactic acid ---> PLA (polylactic acid) + (n-1) water

n CH₃-CH(-OH)-COOH -----> H-(-O-CH(-CH₃)-C(=O)-)_n-OH + (n-1) H₂O

n glucose ---> cellulose or starch or ... + (n-1) water

n C₆H₁₂O₆ -----> H-(-OC₆H₁₀O₄-)_n-OH + (n-1) H₂O​

If, on the other hand, the condensation polymer is made from two separate monomers, each of which is monofunctional but with two occurrences of that single FG, as in the production of PET or nylon-6,6, then there are (2n-1) water molecules produced as a by product:

n hexanedioic acid + n 1,6-diaminohexane ---> nylon-6,6 + (2n-1) water

n HOOC-(CH₂)₄-COOH + n H₂N-(CH₂)₆-NH₂ ----> HO-(-C(=O)-(CH₂)₄-C(=O)-NH-(CH₂)₆-NH-)_n-H + (2n-1) H₂O

n terephthalic acid + n 1,2-ethanediol ---> PET (polyethylene terephthalate) + (2n-1) water

n HOOC-C₆H₄-COOH + n HO-CH₂-CH₂-OH ----> HO-(-C(=O)-C₆H₄-C(=O)-O-CH₂-CH₂-O-)_n-H + (2n-1) H₂O​