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OCR Chemistry F322~ 4th June 2013~ AS Chemistry

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State four ways in which polymers are disposed?

can be used in crackling, recycled AND sorted , can be completely combusted for energy and feedstock for organic chemicals

Reply 2181

geekD96

Original post by simifeltham

C4H7I + OH- ---> C4H7OH + I- and it's nucleophilic because the OH- is an electron rich species due to the minus sign. it's negatively charged because it can donate a pair of electrons.

oh lord now im scared...could you give example for electrophilic then? thanks so much

Reply 2182

simifeltham

Original post by geekD96

can be used in crackling, recycled AND sorted , can be completely combusted for energy and feedstock for organic chemicals

Don't forget landfill sites ( not very environmentally friendly) and forming photodegradable and biodegradable polymers

Reply 2183

Jimmy20002012

How do you find molecular formula if you are given empirical formula :smile:

Posted from TSR Mobile

Reply 2184

IM_SCREWED

omgggggg im so nervous

Reply 2185

fluker6696

Original post by greenmind

Help urgently needed on how to answer question 6 from the Jan'12 paper

Link to the markscheme is http://www.ocr.org.uk/Images/59185-mark-scheme-unit-f322-chains-energy-and-resources-january.pdf

i) The mass of the molecular ion (parent ion) denotes the mass of the molecule - the mass of one electron (negligible). Given that all of the other presented ions are fragment ions, their m/z value must be lower than that of the parent ion. Hence, the mass of the parent ion is the one furthest to the right of the chart.

ii) It is given that the mass of the major fragment ion is 31. You know that the molecule contains C, H and O. Ar (C) = 12, Ar(H) = 1.0 and Ar(O)=16. From here you can see that the easiest way to get to 31 is 1 Carbon atom, 1 Oxygen atom and 3 hydrogen atoms. However, you know that it must be an ion, so there must be a positive charge lying around somewhere (by necessity on either Oxygen or Carbon). Therefore, the answer is CH2OH, where the positive charge lies on the carbon.

iii) You know the mass of the parent ion to be 46. It contains C, H and O. From here you just use trial and error or an equation in harder questions.

iv) As said at the beginning, Ir (M+) = Ar(M) as the mass of an electron is negligible. So you just treat this as a regular RAM question, i.e. (Mass*Abundance)/100

Hope this helps :smile:

Reply 2186

reneetaylor

Original post by JimmyA*

You can just say propene.

Okay, thanks Jimmy.
I was thinking that as the c=c bond is going to involve the first carbon anyway.

I panicked as I thought you had to be precise!

If it's got more than 3 carbons it's safe to start calling compounds but-1-ene or pent-2-ene I think :smile:

Reply 2187

Blashnet

How do you tell is a reaction has homolytic or heterolytic fission? :confused:

Reply 2188

purpleshadows

can some one help me out on 1 i) ii) on the jan 12 paper, how are we suppose know how many without drawing them out??

Reply 2189

simifeltham

Original post by geekD96

oh lord now im scared...could you give example for electrophilic then? thanks so much

Hydration of ethene

C2H4 + HBr ----> C2H5Br

generally anything where a double bond is broken to from a single bond

Reply 2190

geekD96

Original post by Sam_1996

If it involves adding things to a double bond to break the double bond, it's electrophillic
It's nucleophillic if it involves swapping OH for a Halogen

oh okay I gets you so ethane reacting to HBR is electrophilic? and something like (made up) C4H8I + OH- = C4H8OH+I- is nucleophilllic

Reply 2191

Freyaa

Original post by Blashnet

How do you tell is a reaction has homolytic or heterolytic fission? :confused:

Homolytic fission happens in Free radical substitution when one of the atoms has one electron, Heterolytic is like in electrophilic where say bromine has both electrons :smile:

Reply 2192

IM_SCREWED

if from molecular to empirical is simplifying it, shouldn't it just be x ing it to get the molecular?

Reply 2193

geekD96

Original post by simifeltham

Hydration of ethene

C2H4 + HBr ----> C2H5Br

generally anything where a double bond is broken to from a single bond

thanks!!!!!!!!!!!

Reply 2194

MsAqa12345

Original post by Alotties

Sorry its a bit messy!
I can redo it if you need me to :smile:

Thanks so much! I get it now haha :smile:

Reply 2195

simifeltham

Original post by Blashnet

How do you tell is a reaction has homolytic or heterolytic fission? :confused:

Heterolytic the covalent bond brakes and both electrons go to one atom
Homolytic the covalent bond brakes and one electron goes to each carbon forming radicals.

e.g Heterolytic - HBr -> H+ + Br-

Homolytic Cl2 -> Cl. + Cl.

Reply 2196

Beanjamin

Original post by Zzzyax

perhaps someone can help me whats the difference between a alkane and a hydrocarbon, i have lots of revise to do tonight. and what does nucleophile actually mean?

An Alkane is a hydrocarbon because it contains only hydrogen and carbon atoms.

A nucleophile is something that can donate a lone pair of electrons.

Reply 2197

Sam_1996

Original post by simifeltham

State four ways in which polymers are disposed?

-recycle them
-burn them for fuel
-landfill sites
But i can't get a fourth

Reply 2198

Blashnet

Original post by Freyaa

Homolytic fission happens in Free radical substitution when one of the atoms has one electron, Heterolytic is like in electrophilic where say bromine has both electrons :smile:

omg thankyou!! :biggrin:

So any radical has undergone homolytic fission?

Reply 2199

JimmyA*

Here's a few good questions:
Why does the pi-bond break and not the sigma bond?(it's a question which alot of people forget and hasn't come up for a while)
What is the advantage of using the ziegler-natta process over radical polymerisation?
What are the current problems with storing Carbon in stable minerals?