sienna2266
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#1
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Hi guys, just stuck on part cii and ciii. Can someone please help?
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peeked
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Is this for GCSE?
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Bulletzone
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The reaction for polymerisation doesn't really form any waste products apart from the polyalkene product.
Alkene ------> Polyalkene

A 100% atom economy means all atoms in the reactants have reacted to form the product (With no other undesired waste products).
e.g. The Haber process


Where's c iv) ?
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sienna2266
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(Original post by Bulletzone)
The reaction for polymerisation doesn't really form any waste products apart from the polyalkene product.
Alkene ------> Polyalkene

A 100% atom economy means all atoms in the reactants have reacted to form the product (With no other undesired waste products).
e.g. The Haber process


Where's c iv) ?
Hi! so sorry I meant ii and iii
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sienna2266
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(Original post by Bulletzone)
The reaction for polymerisation doesn't really form any waste products apart from the polyalkene product.
Alkene ------> Polyalkene

A 100% atom economy means all atoms in the reactants have reacted to form the product (With no other undesired waste products).
e.g. The Haber process


Where's c iv) ?
Thanks so much for replying! You know where it says "In practice, monomer A cannot be used directly to form PLA because the water produced in the process reacts with the polymer." This is where my confusion stems from. I am not sure what they are trying to say here. Could you please kindly help me with this? Thank you so much!
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Bulletzone
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c ii)

There are 2 types of condensation reactions you will have come across.

Addition Polymerisation
and
Condensation Polymerisation

Energy wise, Addition Polymerisation is preferred. If you do a condensation reaction, water shall be formed. (Hence the name)

You'd have to separate the water from the product which would cost time and money, you also have to ensure you have concentrated sulphuric acid and you may even end up with some unreacted (A). Manufacturers want to save time, money and energy so forming a product without water is preferred.

In the addition polymerisation, you're not losing ANY bonds, all that happens is one of the double bonds becomes a single bond and forms the polyalkene.
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Keira Larkin
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I think I can help you but just to be sure I'm not giving you wrong info can you tell me, for part (i) do the ester bonds get broken?
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Chooxuanwing
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(Original post by sienna2266)
Thanks so much for replying! You know where it says "In practice, monomer A cannot be used directly to form PLA because the water produced in the process reacts with the polymer." This is where my confusion stems from. I am not sure what they are trying to say here. Could you please kindly help me with this? Thank you so much!
Monomer A has both a carboxylic acid and an alcohol functional group. These 2 functional group combine via a condensation reaction to form PLA. and condensation reactions form a waste product, in this case water. This water produced would react with the polymer
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sienna2266
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#9
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(Original post by Bulletzone)
c ii)

There are 2 types of condensation reactions you will have come across.

Addition Polymerisation
and
Condensation Polymerisation

Energy wise, Addition Polymerisation is preferred. If you do a condensation reaction, water shall be formed. (Hence the name)

You'd have to separate the water from the product which would cost time and money, you also have to ensure you have concentrated sulphuric acid and you may even end up with some unreacted (A). Manufacturers want to save time, money and energy so forming a product without water is preferred.

In the addition polymerisation, you're not losing ANY bonds, all that happens is one of the double bonds becomes a single bond and forms the polyalkene.
Thanks so much! In the mark scheme for ii, they specifically talk about water and polymer bonds broken and polymer broken down/lost - so is the condensation reaction in A to form PLA and water a reversible reaction where the water produced goes on react as in hydrolyse the PLA back to its carboxylic acid and alcohol components or is it to do with something else?
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sienna2266
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#10
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(Original post by Chooxuanwing)
Monomer A has both a carboxylic acid and an alcohol functional group. These 2 functional group combine via a condensation reaction to form PLA. and condensation reactions form a waste product, in this case water. This water produced would react with the polymer
Thanks so much! In the mark scheme for ii, they specifically talk about water and polymer bonds broken and polymer broken down/lost - so is the condensation reaction in A to form PLA and water a reversible reaction where the water produced goes on react as in hydrolyse the PLA back to its carboxylic acid and alcohol components or is it to do with something else?
Attachment 742510
Have just attached what it says in the ms along with the guidelines bit
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Chooxuanwing
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(Original post by sienna2266)
Thanks so much! In the mark scheme for ii, they specifically talk about water and polymer bonds broken and polymer broken down/lost - so is the condensation reaction in A to form PLA and water a reversible reaction where the water produced goes on react as in hydrolyse the PLA back to its carboxylic acid and alcohol components or is it to do with something else?
Attachment 742510
Have just attached what it says in the ms along with the guidelines bit
Yes, the water produced might hydrolyze the polymer back into its monomer
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sienna2266
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#12
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(Original post by Chooxuanwing)
Yes, the water produced might hydrolyze the polymer back into its monomer
Thanks so much and for part iii) Why does it say "DO NOT ALLOW no molecule lost from B" - do you get this? Many thanks
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Chooxuanwing
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#13
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#13
(Original post by sienna2266)
Thanks so much and for part iii) Why does it say "DO NOT ALLOW no molecule lost from B" - do you get this? Many thanks
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Why is it more environmentally friendly, this is because even though IF a molecule(water) is lost from B, water does not harm the environment
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