AQA AS Chemistry: 8th June Watch

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thefish_uk
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Anybody else got this? I've got modules 2 and 3 tomorrow.

How is revision been going? I think each person ought to set the next a question just as a revision thing.

OK, so first one from module 3...

What's the conditions, mechanism and products for catalytic cracking?
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princessmarisa
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Hey I am just retaking Mod3.

Catalytic cracking :-

High Temp, Carbocation intermediate mechanism, products are branched chain alkanes, alkenes and armatic hydrocarbons.


q. How do you change a primary alcohol into a carboxylic acid, reagents,catalysts,condtitions etc.?
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Kiesha
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(Original post by marisad_uk)
q. How do you change a primary alcohol into a carboxylic acid, reagents,catalysts,condtitions etc.?
Use an excess of acidified potassium dichromate (oxidising agent) under reflux conditions.

Q: Advantages/Disadvantages of producing ethanol by
- direct hydration
- fermentation?
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Scottus_Mus
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(Original post by Kiesha)
Q: Advantages/Disadvantages of producing ethanol by
- direct hydration
- fermentation?
Fermentation: Renewable Source, Slow Reaction Rate, Impure Product Produced, Batch Process (Cheap On Equip;Expensive Manpower)

Hydration: Finite Resourece, Fast Reaction, Pure Product, Continuous Process (Expensive Equip;Cheap Manpower)
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princessmarisa
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fermentation - ad. more renewable source, low tech equpiment for process and distillation after.easier and less expensive to maintain conditions (lower temp & pressure)disad- batch process so production costs high to get same yield. After a certain amount of ethanol is produced the environment is too toxic for the zymase and the forward reaction stops, causing product purity of about 15%

direct- 95% purity, continuous process
disad.high costs to maintain high temps high pressure and high tech equipment.

What is

A chain isomer?
A position isomer?
A geometric isomer?
A optical isomer?

are there any other isomers?
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wednesburywench
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advantages of hydration = faster, purer products, less expensive on manpower
advantage of Fermentation = Cheaper on machinary, and renewable energy source

(hope im right!!)

question- Write equations to illustrate how berylium hydroxide reacts with both an acid and a base. What is this atypical nature called?

(by the way is it me or has Aqas site gone down!!!I need the answer to this question!!!)
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Kiesha
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We don't need to know optical isomers for AS ... and I'm going to go and revise the definitions for the others cos I can't remember them!
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princessmarisa
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(Original post by Kiesha)
We don't need to know optical isomers for AS ... and I'm going to go and revise the definitions for the others cos I can't remember them!
Are you sure I learnt it for AS its in my AS book and i am pretty sure it is in the spec.
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princessmarisa
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(Original post by wednesburywench)
advantages of hydration = faster, purer products, less expensive on manpower
advantage of Fermentation = Cheaper on machinary, and renewable energy source

(hope im right!!)

question- Write equations to illustrate how berylium hydroxide reacts with both an acid and a base. What is this atypical nature called?

(by the way is it me or has Aqas site gone down!!!I need the answer to this question!!!)
Hey i thought we were doing module 3, and i recognise that from module 1 double check your spec i am 99.9% sure beryllium was removed from it so you don't have to know that at all ( i took mod 1 in jan)
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wednesburywench
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no we dont, you just need to know that optical isomers are a type of sterioisomers, the rest comes in module 4
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Kiesha
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(Original post by wednesburywench)
advantages of hydration = faster, purer products, less expensive on manpower
advantage of Fermentation = Cheaper on machinary, and renewable energy source

(hope im right!!)

question- Write equations to illustrate how berylium hydroxide reacts with both an acid and a base. What is this atypical nature called?

(by the way is it me or has Aqas site gone down!!!I need the answer to this question!!!)
Amphoteric = can act as both acid and base.

Base: Be(OH)2 + H2SO4 --> BeSO4 + 2H20

Acid: Be(OH)2 + 2OH- --> Be(OH)42-
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wednesburywench
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the equation iv got for the acid is be(OH)2 + 2H+ + 2H20 --> Be(H2O)4 with the 2+.

Is this acceptable aswell?
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Kiesha
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(Original post by marisad_uk)
Hey i thought we were doing module 3, and i recognise that from module 1 double check your spec i am 99.9% sure beryllium was removed from it so you don't have to know that at all ( i took mod 1 in jan)
Do you mean that we don't have to know Beryllium for Mod 1? In my spec it says we do but I don't know what year it's from :confused:
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princessmarisa
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Look at the top of your spec or in small print at the bototm it will say somewhere. I took mod1 in jan and it was def not on the jan spec are they allowed to put it back in for june?
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Kiesha
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(Original post by wednesburywench)
the equation iv got for the acid is be(OH)2 + 2H+ + 2H20 --> Be(H2O)4 with the 2+.

Is this acceptable aswell?
I'm not sure, sorry. There's another version in my textbook:

Be(OH)2 + 2H+ ---> Be2+ + 2H2O
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Kiesha
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(Original post by marisad_uk)
Look at the top of your spec or in small print at the bototm it will say somewhere. I took mod1 in jan and it was def not on the jan spec are they allowed to put it back in for june?
:eek: Mine's from 2001/2002! Hmm can't even check on the AQA website since it's down :mad: Oh and I doubt they would have changed it from Jan to June.
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sahmed786
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(Original post by Kiesha)
Do you mean that we don't have to know Beryllium for Mod 1? In my spec it says we do but I don't know what year it's from :confused:
be is off the syllabus now.


it got removed this year
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wednesburywench
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its down i need to check sumat too arghhhhhhhh. im gona go with the ionic equation you just put thats defo right iv seen it b4.
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princessmarisa
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(Original post by Kiesha)
:eek: Mine's from 2001/2002! Hmm can't even check on the AQA website since it's down :mad: Oh and I doubt they would have changed it from Jan to June.
I always get the most up to date spec for any mods I take, becasue they remove laods every year and there is no point revising stuff you don't need
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thefish_uk
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(Original post by Kiesha)
:eek: Mine's from 2001/2002! Hmm can't even check on the AQA website since it's down :mad: Oh and I doubt they would have changed it from Jan to June.
Hmmmmmmm does anybody have a mark scheme for AQA Jan 2004 Chem2+3? AQA website is down. GRRRRRRRR!!!!!!!!!
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