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# AS chemistry - post here if need help watch

1. Explain how a hetrogeneous catalyst provides a different pathway for reactions with a lower activation energy. Help anyone?
2. (Original post by Roth)
Explain how a hetrogeneous catalyst provides a different pathway for reactions with a lower activation energy. Help anyone?
not really sure about this one. but i think its got sth to do with providing a greater surface area...
3. This is a very vague question but what is the best way to remember all the reagents and conditions for the organic chemistry module. IS there a website where they are all simplified onto a table or something like that. Or do i have to go theough my notes and look for each one.

Many thanks if u cud help
4. (Original post by KOH)
DATA:
4NH3(g) + 5O2(g) ---------> 4NO(g) + 6H2O(l) (Delta H = -1170 KJ )

4NH3(g) + 3O2(g) ----------> 2N2(g) + 6H2O(l) (Delta H = -1530 KJ )

2H2(g) + O2(g) ----------------> 2H2O(l) (Delta H = -576 )

(a) Find the enthalpy of formation of ammonia.
(b) Calculate of formation of Nitrogen monoxide.
Not sure if you still need help on this, as the method and answer to part (a) has been explained much better than I could ever do it. Apply the same principle - we know what DeltaH for NH3 is, the same for H2O, and that H is 0 for unchanged elements. So: write the starting materials, 4N2(g), 5O2(g) and 6H2(g). This then goes to 4NH3(g) with H=-198kJ and 5O2(g) with H=0. These 'reactants are then conveted to 4NO and 6H2O, and we know that H for this conversion is -1170kJ. We know that H for the water formation is 3times -576. Therefore -198+(-1170) must = -1728+x, where x=4times H[NO]. Hence H[NO] = +90kJ/mol
HTH
5. (Original post by Roth)
Explain how a hetrogeneous catalyst provides a different pathway for reactions with a lower activation energy. Help anyone?
Heterogenous catalyst is a catalyst in a different phase to the reactants
an example could be addition of H2 to an alkene (eg ethene) with Nickel catalyst- which is a solid, while the reactants are gaseous.
-The reactants ADSORB onto the nickel surface
-Molecules are brought together
-Active sites involved
-And finally products are DESORBED

~something like that
6. (Original post by confusd_puzzled)
This is a very vague question but what is the best way to remember all the reagents and conditions for the organic chemistry module. IS there a website where they are all simplified onto a table or something like that. Or do i have to go theough my notes and look for each one.

Many thanks if u cud help
Anyone?
7. (Original post by confusd_puzzled)
Anyone?
A decent text book should have a chart showing organic synthesis routes.
8. confusd_puzzledThis is a very vague question but what is the best way to remember all the reagents and conditions for the organic chemistry module. IS there a website where they are all simplified onto a table or something like that. Or do i have to go theough my notes and look for each one.

Many thanks if u cud help

yeah that's a pain. best way to revise those is make a flow chart/spider web or table as 'revision notes' -not put anythign detailed but some quick points and keep them easily accessible.
9. Does mental help count? I've got AH chemistry at 9AM on Wednesday, so I've basically got tomorrow left to revise. I'm ******** myself, help!
10. wow this thread went down hill after i left
i wonder if i am on anyone's ignore list?
11. Unfortunately I had to go and do some work (exams start on Thursday), so that meant switching off the computer - this forum is too distracting. Actually, its stopping me working now!
12. (Original post by chrisbphd)
Unfortunately I had to go and do some work (exams start on Thursday), so that meant switching off the computer - this forum is too distracting. Actually, its stopping me working now!
yeah know that feeling all to well
13. (Original post by confusd_puzzled)
This is a very vague question but what is the best way to remember all the reagents and conditions for the organic chemistry module. IS there a website where they are all simplified onto a table or something like that. Or do i have to go theough my notes and look for each one.

Many thanks if u cud help
theres no best way... jus take notes and remember them
14. I found that the best way was to write them out, with mechanisms, time after time until you know them.
15. (Original post by chrisbphd)
I found that the best way was to write them out, with mechanisms, time after time until you know them.
mechanisms arent required for AS chemistry.
16. (Original post by z!D4N)
mechanisms arent required for AS chemistry.
Yes they are. For OCR Module 2, at least.
17. (Original post by mongoose)
Yes they are. For OCR Module 2, at least.
this is a topic for AS chemistry. - -
18. They are required for module 3 AQA (AS), and module 2 OCR is AS.
19. (Original post by chrisbphd)
They are required for module 3 AQA (AS), and module 2 OCR is AS.
but are they called Advanced Subsidary level tho?
20. (Original post by daydream)
I never said i was a doctor? but it's cool to get praized by someone which thinks i'm a doctor haha
hmmmmmm

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