AQA AS Chemistry: 8th June

2

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.?

Reply 2

10

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?

Reply 3

Scottus_Mus

1

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)

Reply 4

2

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?

Reply 5

2

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!!!)

Reply 6

10

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!

Reply 7

2

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.

Reply 8

2

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)

Reply 9

2

no we dont, you just need to know that optical isomers are a type of sterioisomers, the rest comes in module 4

Reply 10

10

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)₄^2-

Reply 11

2

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

Is this acceptable aswell?

Reply 12

10

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:

Reply 13

2

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?

Reply 14

10

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

Reply 15

10

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?

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.

Reply 16

sahmed786

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

Reply 17

2

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.

Reply 18