OCR AS - Chemistry Unit F322 - Chains, energy and resource - REVISION!

Hey guys what do you think the level of difficulty for this paper will be like....I've got predominantly A's in most practice papers but there have been one or two exceptions like the Jan 2010 and Jan 2011 paper in which I got solid B's....so do you think this paper will be a fairly standard paper based on previous years?

it goes like hard, easy/middle, hard

who knows?

=/ i find all of them equally hard

Reply 261

Eat.Sleep.Row.Repeat.

8

Original post by KateSW

Polymers can be combusted for energy, or melted and remoulded for other plastics.
CFC's are being reduced (due to the Montreal protocol) and replaced by HFC's (which are much much slower at depleting the ozone)

did I miss anything?

What are the pros and cons of steam hydration over fermentation to produce ethanol?

You could say for Polymers: Researching into photo/biodegradeable polymers. Sorting and recycling. And for the CFC's you need to explain why they're much slower. It's because of the carbon-hydrogen bond which is weaker than the carbon-halogen bonds, and therefore it is broken down much quicker and the CFC part then reacts :smile:

Reply 262

KateSW

Original post by Dave_Beeston

You could say for Polymers: Researching into photo/biodegradeable polymers. Sorting and recycling. And for the CFC's you need to explain why they're much slower. It's because of the carbon-hydrogen bond which is weaker than the carbon-halogen bonds, and therefore it is broken down much quicker and the CFC part then reacts :smile:

ooh thanks, all really good points!

Do people want to keep asking questions?
-Define specific heat capacity

-If a reaction is endothermic, what is the sign (+/-) of the enthalpy change?

-Which way does the equilibrium shift if the pressure is increased for the Haber process N2 + 3H2 --> 2NH3 (the arrow is meant to be an equilibrium sign :s-smilie:

)

Reply 263

peaches1

any guesses what will come in? there could be something on boltzman distibution

Reply 264

supersping

has anyone got any practice exam questions? need desperately!

Reply 265

DoDoBeDo

I'm going to sit here & pray that there's a nice 11 marker that includes a Boltzman & an enthalpy profile diagram. :lol:

I'd like for a longer question on the consequences of greener chemistry... A reasonably easy question that involves curly arrows. & a generous mas spec/infared one :biggrin:

They'd be my ideal 'longer' questions, I feel I could get all the marks given those questions an then pick up the rest around them.

I'm not feeling too confident about this though :frown:

If there's not the long question on Botzmann I may cry haha

Right. Must revise my conditions for experiments & what way equilibrium moves given certain conditions... Has anyone got any good ways to remember these or is it just you know them or you don't? =\

Reply 266

touran22

Original post by DoDoBeDo

Right. Must revise my conditions for experiments & what way equilibrium moves given certain conditions... Has anyone got any good ways to remember these or is it just you know them or you don't? =\

Basically: -------------- Endo-------------- Exo

Temp Increase RHS ----------- LHS

Temp Decrease LHS ---------- RHS

---------------- Fewer molecules on RHS ------------------ More molecules on RHS

Pressure increase ---------------- RHS -------------------- LHS

Pressure decrease --------------- LHS ------------- RHS

Remember this like i have and all those questions become easy !

(edited 12 years ago)

Reply 267

Dave 1994

Original post by Dave_Beeston

You could say for Polymers: Researching into photo/biodegradeable polymers. Sorting and recycling. And for the CFC's you need to explain why they're much slower. It's because of the carbon-hydrogen bond which is weaker than the carbon-halogen bonds, and therefore it is broken down much quicker and the CFC part then reacts :smile:

Do you mean for the HCFCs?

And its the Cl radical that reacts with ozone, not CFCl radicals

I'd just assumed it was because a HCFC forms less Cl radicals than a CFC when subject to UV light :\

However, after a little research found this:

"HCFCs have shorter atmospheric lifetimes than the CFCs and a much smaller capacity to deliver reactive chlorine to the stratosphere where the ozone layer is found." from http://www.environment-agency.gov.uk/business/topics/pollution/684.aspx

So the main reason actually seems to be that they are less likely to reach the ozone layer in order to release Cl radicals there :smile:

Reply 268

Dave 1994

Original post by DoDoBeDo

Right. Must revise my conditions for experiments & what way equilibrium moves given certain conditions... Has anyone got any good ways to remember these or is it just you know them or you don't? =\

Just remember that whatever you do to a system in equilibrium, it tries to do the opposite (our teacher calls it the law of awkwardness :P)

So if you heat it, the system will try to get colder so the equilibrium will move in the direction of the endothermic reaction, so the system gets colder.

This also works in the same way for pressure and concentration. :smile:

Reply 269

786girl

ive got the unit 1 today...anyone else?

Reply 270

akydon619

Original post by kingam

how many marks did you get for CW

38/40

Reply 271

Killjoy-

8

Original post by KateSW

ooh thanks, all really good points!

Do people want to keep asking questions?
-Define specific heat capacity

-If a reaction is endothermic, what is the sign (+/-) of the enthalpy change?

-Which way does the equilibrium shift if the pressure is increased for the Haber process N2 + 3H2 --> 2NH3 (the arrow is meant to be an equilibrium sign :s-smilie:

)

- Is it the energy required to raise the temperature of one gram of a substance to 1degree C?
- Positive
- Shifts to the right (In the direction of the forward reaction)

Reply 272

TrampingRampage

Can someone compile a list of all the catalysts along with the reactions they're involved in and if relevant also the temperature etc.. :smile:

Reply 273

arvin_infinity

3

Original post by TrampingRampage

Can someone compile a list of all the catalysts along with the reactions they're involved in and if relevant also the temperature etc.. :smile:

That ll be epic ! Probably the only way to get your head around them :wink:

Based on the exam I had today..it might not be a easy paper and details might feature heavily

Reply 274

ChessMister

12

Original post by TrampingRampage

Can someone compile a list of all the catalysts along with the reactions they're involved in and if relevant also the temperature etc.. :smile:

bits in brackets are not essentials

Cracking- Zeolite Catalyst (450 deg.)
Haber Process- Iron, 200 atm, 450 deg.
Hydrogenation- Nickel
Hydration- Phosphoric Acid, 300 deg, 100 atm
Esterification- Sulphuric Acid
Breakdown of Ozone- Cl radicals (or any other halogen radicals)

Don't know if I've missed any

(edited 12 years ago)

Reply 275

supersping

heyy need help!

how do you work out enthalpy change of formation when you are giving combustion data?

Reply 276

shuty

9

Original post by kingam

do you ahve any other questions

mmmm what do we need 2 know about module 4? we havn't covered that section in lessons and the books sooooooooooooooooooo boring... i mean the stuff on CCS and all that :biggrin:

... you can ask me questions for a change next time :rolleyes:

i might be able to help.... :smile:

Reply 277

Phenylethylamine_

Original post by ChessMister

bits in brackets are not essentials

Cracking- Zeolite Catalyst (450 deg.)
Haber Process- Iron, 200 atm, 450 deg.
Hydration- Nickel
Hydrogenation- Phosphoric Acid, 300 deg, 100 atm
Esterification- Sulphuric Acid
Breakdown of Ozone- Cl radicals (or any other halogen radicals)

Don't know if I've missed any

Hydrogenation requires a nickel catalyst (150 deg) and Hydration requires the phosphoric acid catalyst with high pressure and temperature, you got them two the other way around :tongue:

Also, not sure where you got the 300 deg and 100atm from? For hydration of the ethene i.e. making ethanol, requires 300 deg and 60atm. :wink:

Reply 278

ChessMister

12

Original post by Phenylethylamine_

Hydrogenation requires a nickel catalyst (150 deg) and Hydration requires the phosphoric acid catalyst with high pressure and temperature, you got them two the other way around :tongue:

Also, not sure where you got the 300 deg and 100atm from? For hydration of the ethene i.e. making ethanol, requires 300 deg and 60atm. :wink:

For hydration various markschemes have given it as 100-200, contrasting the 60 atm in the book. Never seen it as low as 60

Reply 279

Phenylethylamine_

Original post by ChessMister

For hydration various markschemes have given it as 100-200, contrasting the 60 atm in the book. Never seen it as low as 60

Ahh okay, because in theofficial/course textbook, on the first page of 2.2 for the hydration of ethene, it says 60atm?

OCR AS - Chemistry Unit F322 - Chains, energy and resource - REVISION!

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