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OCR Chemistry F322~ 4th June 2013~ AS Chemistry

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Can someone please explain the shifts for equilibrium (le chateliers priniple and the haber process and that stuff)??
Guys, could you help me with reagents and conditions of different reactions? :frown:
Original post by walkers38
Guys, could you help me with reagents and conditions of different reactions? :frown:


Which reactions are you struggling with?
Original post by walkers38
I have been scanning through some old past papers. And here are some new type of long answer q's.

* Explain how CCl2F2 in the stratosphere alter the balance of oxygen and ozone. You should include equations in your answer. [6]
* Describe, using one example in each case, the different modes of action of homogeneous and heterogeneous catalysis. [10]
* Outline how ethanol is produced industrially from sugars and from ethene. Comment on the decisions that a company needs to consider when deciding which of these methods to use. [8]
* Outline the processes of how components obtained from fractional distillation are refined with aid of suitable equations. State the importance of products formed in each process [8]

Some not so long, but tricky q's.
* Explain the greenhouse effect [3]
* State two environmental consequences of the presence of nitrogen monoxide
* Explain with reasons two uses of CCl2F2 [2]
* In the conditions often used in the Haber process, there is only a 15% yield of ammonia. Suggest what happens to any unreacted nitrogen and hydrogen. [1]



If you want answers, just ask me :smile:


What would you talk about for the second question?

And for the second one would you compare the methods of fermentation to the reaction of ethene and steam in terms of waste products (atom economy) and percentage yield?

also for the fourth question, what is the importance of the products formed in the process - besides them being used as fuel.
Original post by walkers38
I have been scanning through some old past papers. And here are some new type of long answer q's.

* Explain how CCl2F2 in the stratosphere alter the balance of oxygen and ozone. You should include equations in your answer. [6]
* Describe, using one example in each case, the different modes of action of homogeneous and heterogeneous catalysis. [10]
* Outline how ethanol is produced industrially from sugars and from ethene. Comment on the decisions that a company needs to consider when deciding which of these methods to use. [8]
* Outline the processes of how components obtained from fractional distillation are refined with aid of suitable equations. State the importance of products formed in each process [8]

Some not so long, but tricky q's.
* Explain the greenhouse effect [3]
* State two environmental consequences of the presence of nitrogen monoxide
* Explain with reasons two uses of CCl2F2 [2]
* In the conditions often used in the Haber process, there is only a 15% yield of ammonia. Suggest what happens to any unreacted nitrogen and hydrogen. [1]



If you want answers, just ask me :smile:

What are homogeneous and heterogeneous catalysts??
Original post by simifeltham
Which reactions are you struggling with?


ALL. It changes in every question.

For e.g. Bromopropane elimination reaction with OH ions. What's the product, reagent and conditions for this reaction?


Others are:
* Dehydration
* Esterification
* Hydrogenation
* Hydration
Reply 2366
Avatar for XiLE
XiLE
Original post by helenabrennan
Can someone please explain the shifts for equilibrium (le chateliers priniple and the haber process and that stuff)??


If reaction is endothermic:

Endothermic direction is on the right
Exothermic direction is on the left

If reaction is exothermic:

Exothermic direction is on the right
Endothermic direction is on the left

Le Chatelier's principle - when a factor governing the position of equilibrium is altered, the system moves in a way which opposes the initial change.

For example, if you increase the pressure of a reaction, the system will decrease the pressure and the equilibrium will move to the area with fewer gaseous particles (measured via moles of the reactants & products).
Reply 2367
Avatar for bluedate
bluedate
Original post by helenabrennan
Can someone please explain the shifts for equilibrium (le chateliers priniple and the haber process and that stuff)??


Okay ermm when you increase the temperature, the equilibrium will shift to the endothermic reaction e.g. if forward reaction is exothermic, then high temp will shift it to the left (reverse)

If you increase the pressure the equilibrium will shift to the side with fewest gaseous molecules, if you decrease the pressure the equilbrium will shift to the side with the most gaseous molecules

:smile: hope that helps
Describe, using one example in each case, the different modes of action of homogeneous and heterogeneous catalysis. [10]
homogeneous: catalyst in same phase as reactants ¸;
heterogeneous: catalyst in different phase as reactants ¸
homogeneous: any example, e.g. Cl in ozone breakdown ¸
mode of action to match example: forms a intermediate/ClO ¸
propagation stages shown ¸
overall equation ¸
heterogeneous: any example, e.g. Fe in Haber process ¸
mode of action to match example: reactants adsorbed on surface of catalyst ¸
weakens bonds in reactants ¸
reaction takes place and products diffuse from surface of catalyst ¸
Reply 2369
Avatar for wndms
wndms
1
How does IR spec work?

Posted from TSR Mobile
Original post by wndms
How does IR spec work?

Posted from TSR Mobile


That's the most easy peasy bit of chemistry. Just look at major peaks and check the data sheet and state the bonds they represent. (or ABSENCE of bonds in some case)
Original post by shomshomni
What are homogeneous and heterogeneous catalysts??


homogeneous - catalyst with the same physical state as reactants
heterogeneous - catalyst with a different physical state as reactants
Revision


June 2010 Question 6 c i


Link : http://www.ocr.org.uk/Images/65130-question-paper-unit-f322-chains-energy-and-resources.pdf


Please help and reply soon

It's only a marker! and I seem to not get it... ^_^

THANK YOU!!!! :biggrin:
Original post by walkers38
ALL. It changes in every question.
For e.g. Bromopropane elimination reaction with OH ions. What's the product, reagent and conditions for this reaction?

We dont have to know that.
Others are:
* Dehydration - Dehydration of an alcohol gives you alkene and h20 , h2so4 reflux
* Esterification - H2SO4 REFLUX, CH2OH + CH3COOH = CH3COOCH3
* Hydrogenation - 150C, Ni catalyst C2H4 + H2 = C2H6
* Hydration - 300C, 60atm , H3PO4 C2H4 + STEAM = C2H5OH
Good night guys!! Have good sleep and THANK GOD it's in the afternoon so we have more time!
Reply 2375
Avatar for wndms
wndms
1
What are the purpose of IR?
To find functional groups and...?

Posted from TSR Mobile
Reply 2376
Avatar for XiLE
XiLE
Original post by Jacksgap
Revision


June 2010 Question 6 c i


Link : http://www.ocr.org.uk/Images/65130-question-paper-unit-f322-chains-energy-and-resources.pdf


Please help and reply soon

It's only a marker! and I seem to not get it... ^_^

THANK YOU!!!! :biggrin:


I was stuck too, I couldn't find the formula for this answer, but I used trial and error. :L

((2.5x105) x 909)/4 = 56812500 KJ

4 comes from the 4NO
and 909 comes from the Delta H value.
Reply 2377
Avatar for SheriB
SheriB
9
Original post by d.adrian
yep do you want it? Can send it over email if you want:smile:

Its okay someone put it up. thanks anyway
Reply 2378
Avatar for SheriB
SheriB
9
Original post by simifeltham
Here JAN13

thank you
Reply 2379
Avatar for bluedate
bluedate
Original post by Jacksgap
Revision


June 2010 Question 6 c i


Link : http://www.ocr.org.uk/Images/65130-question-paper-unit-f322-chains-energy-and-resources.pdf


Please help and reply soon

It's only a marker! and I seem to not get it... ^_^

THANK YOU!!!! :biggrin:


Examiner report says:
Only a small proportion of the candidates in (i) realised that the 909 kJ of heat released
comes from 4 mol of NO; so the correct answer was 5.68 × 107 kJ

So basically 2.50x10^5 / 4 then x 909 :smile:

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