OCR AS Salters Chemistry F332 - Wednesday 23rd May 2012 1:30pm

Thank you very much! That's very helpful

Could you also tell me how branching affects flexibility ?

any answers to these questions ?
and is your teacher quite confident?
Thank you very much

Some questions my teachers gave me that she thought might come up:

1. What key properties does polythene have that makes it suitable for bottles, electrical insulation and hip and bone replacements?
2. Why did Gibson and Fawcett attempt to make their benzenecarbaldehyde under such high pressures?
3. Why did the pressure reduce in the reaction vessel despite their not being a leak?
4. Draw an energy level diagram for the decomposition of ethene to carbon.
5. What is a free radical?
6. What type of bong breakage (fission) occurs in the organic peroxide during the initiation step of the mechanism?
7. What does the ‘curly arrow’ represent in the diagram at the bottom of page 3?
8. What type of reaction:
[INDENT]a. Increases the chain length of the polymer by one ethene unit?
b. Stops the growth of the chain?[/INDENT]
9. Why can polythene be described as a thermoplastic – use evidence from the description of its use on page 4.
10. What is a catalyst and how does it allow lower pressures and temperatures to be used?
11. Describe the mechanism by which these modern catalysts probably work.
12. What is the principle intermolecular bond between polythene chains?
13. Describe how these bonds come about?
14. Why does branching produce a lower density polymer?
15. How will the branching affect the melting point of the polymer?
16. What environmental issues are there related to the disposal of plastic waste?

1. Polythene is water resistant, flexible and unreactive. It also doesn't decompose easily, is a good insulator and is a thermoplastic so it can be easily moulded into different shapes.
2. They wanted to shift the equilibrium of the reaction to the right and increase the yield of the ketone that was produced when ethene and benzaldehyde reacted.
3. Ethene was being polymerised (not completely sure how this happens, I think it's to do with peroxide initiating the reaction).
4. Draw the relevant diagram.
5. A free radical is an atom, molecule or ion with unpaired electrons.
6. Homolytic fission.
7. One electron going to the Ethane and one electron going to the free radical.
8. a) Propagation.
8. b) Termination.
9. Not too sure what the answer to this is, will update if someone has a good answer.
10. A catalyst lowers the activation enthalpy for a reaction to take place. It provides an 'alternate route' for the reaction. Without a catalyst the colliding particles require a higher amount of energy for the reaction to occur so increasing the temperature gives the particles more of a chance of having the required energy. With a catalyst the energy they require is less thus a lower temperature can be used. A lower pressure can be used because a catalyst naturally increases the speed of the reaction so you do not need to try and speed it up further.
11. The catalyst adsorbs the molecule, breaks its bonds, makes new ones and then releases it. (requires a bit more detail)
12. Instantaneous Dipole - Induced Dipole
13. At a certain moment in time the electrons may be closer to one of the nucleus which will change the polarity of the molecule and instantaneously create a dipole. This dipole will repel or attract the electrons in nearby molecules creating induced dipoles. (probably requires some editing).
14. Density is is the amount of mass per unit volume. If a polymer has branching it will be harder for chains of them to 'neatly slot' together meaning that there is less mass per unit volume so it is a lower density polymer.
15. Due to the polymer being less tightly packed the intermolecular bonds are fewer so less energy is required to separate the chains.
16. Plastics can degrade very slowly or not decompose at all. This means that they take up places in landfill sites and will remain there indefinitely.

Undoubtedly I've made mistakes or not given the perfect answers to these questions so if anyone has any better answers I'll update these with them.

My teacher reckons a good 50-75% of the questions will be based around those, might not be though.

Amazing help, thank you soo much !!
Helps alot !!
Also do u have the Jan 2012 paper and mark scheme ?
http://www.scribd.com/doc/79256965?secret_password=lh4oog7hqi4oynpdlvy
Got the paper ^
But not the mark scheme
Thanks again!!

hey guys
you know for the pre release question in may 2011 for drawing polybutadiene, how come there is a double bond ?

I just did a paper where it asked for the aqueous reagant used, and the colour change you would see, so what section of work is this under so I can revise it? If possible could you also write down all the reagents we could be asked in case I have lost my notes on it

Thanks

Look at my post above and a few pages back i uploaded a pdf outlining all of the reagents. But here it is again.

Look at my post above and a few pages back i uploaded a pdf outlining all of the reagents. But here it is again.

This sheet is missing quite a few things and there are some incorrect details. I've been through every past paper and if you used this sheet you'd lose quite a few marks. For example, for the oxidation reactions in that table, you need (acidified) sulfuric acid as well as potassium dichromate. For alcohol to chloroalkane, the condition is high temp, not room temp. For primary alcohol to aldehyde, the condition is only distil, not heat and distil. I think everything else looks okay though, but I've never seen a question come up about the nitrile.

Found it on TSR the other day, can't remember who uploaded it but:

http://www.thestudentroom.co.uk/attachment.php?attachmentid=149379&d=1337442261

This sheet is missing quite a few things and there are some incorrect details. I've been through every past paper and if you used this sheet you'd lose quite a few marks. For example, for the oxidation reactions in that table, you need (acidified) sulfuric acid as well as potassium dichromate. For alcohol to chloroalkane, the condition is high temp, not room temp. For primary alcohol to aldehyde, the condition is only distil, not heat and distil. I think everything else looks okay though, but I've never seen a question come up about the nitrile.

You do get the mark by just saying acidified. As it can be different acids.
You wouldn't lose a mark my saying heat and distill, as to distill you need to heat it... But I guess to be safe maybe don't say heat.
Never seen a question on nitrile, hints at remember that one imo

I think your right about chloroalkane

What is it missing? (for AS)