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OCR Salters Chemistry F335 12th June 2013 Exam revision thread

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Reply 660
Avatar for Sujman
Sujman
1
Original post by Futuristicmedic
I reckon A = 85/120 ?


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What about a*
Original post by A.Mustapha
For the radical question, did people get
Initiation : CH4 --> CH3 + H

Termination: CH3 + CH3 --> C2H6


Yeah I got that equation, but... a) does it matter which side the dot goes? I can't remember where I put it.. And b) did you have to label them initiation and termination because if so I didn't read the question.. :/
Reply 662
Avatar for ells-13
ells-13
Was there a question asking to classify the reaction, condensation or addition and a reason for it???
Reply 663
Avatar for Reina
Reina
8
Original post by suncake
Isn't it divide by 2?



But then the salt:acid conc ratio is still 2:1? Water dilutes them both so no effect?

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Sticking random numbers in to help explain:

I was thinking if you start off with 100 salt and 100 acid. Then half the acid is neutralised to form 50 acid and 50 salt which is added to the original salt. So you end up with 150 salt divided by 50 acid. So the ratio is 3?
Reply 664
Avatar for C.JTop
C.JTop
5
Original post by HTB
what did people put for the 'industrial use of hydrogen'? (i think that was the question!)


making hcl
Original post by hayleyvictoria
Hehee, looking down this thread, I don't know why i do this to myself, so many silly mistakes.. :frown:


Coming out of the exam... :thumbsup:

Talking with classmates... :unsure:

On TSR... :zomg:
Reply 666
Avatar for C.JTop
C.JTop
5
Original post by ells-13
Was there a question asking to classify the reaction, condensation or addition and a reason for it???


addition 100% yield
Original post by ells-13
Was there a question asking to classify the reaction, condensation or addition and a reason for it???


This was really misleading, jumping straight into it I saw an amide link and put condensation. After looking at it more carefully I noticed nothing had been lost from the monomers, and also the question after stated it was 100% atom economy - so had to be addition.
Reply 668
Avatar for manpyy
manpyy
Original post by Pandora's Box
Yeah I got that equation, but... a) does it matter which side the dot goes? I can't remember where I put it.. And b) did you have to label them initiation and termination because if so I didn't read the question.. :/


the dot doesn't matter and it asked in the question for the type of radical reaction, i missed it that when i did the equation but saw that it was worth four marks so i read the questions again and saw it
Original post by Sujman
What about a*


Is it not just 90% so maximum of 107/120 if there was no cap of full UMS?
Original post by abzy1234
Coming out of the exam... :thumbsup:

Talking with classmates... :unsure:

On TSR... :zomg:


Story of my life!
Original post by suncake

But then the salt:acid conc ratio is still 2:1? Water dilutes them both so no effect?

Posted from TSR Mobile

Oh I do hope so! Thanks! :smile:
Reply 672
Avatar for suncake
suncake
14
Original post by Reina
Sticking random numbers in to help explain:

I was thinking if you start off with 100 salt and 100 acid. Then half the acid is neutralised to form 50 acid and 50 salt which is added to the original salt. So you end up with 150 salt divided by 50 acid. So the ratio is 3?


Acid + salt = water, though!

I put exactly the same curly arrows as you. :redface:

Posted from TSR Mobile
Reply 673
Avatar for ells-13
ells-13
Original post by billybobs
This was really misleading, jumping straight into it I saw an amide link and put condensation. After looking at it more carefully I noticed nothing had been lost from the monomers, and also the question after stated it was 100% atom economy - so had to be addition.


Ye addition:smile: but my reason was no small molecule was eliminated, is that right?
Reply 674
Avatar for Reina
Reina
8
Original post by ells-13
Was there a question asking to classify the reaction, condensation or addition and a reason for it???


I think there was a "is this addition or a condensation" question as well as a "classify this reaction question" but I can't remember what kind of reactants were involved :s-smilie:

I think I put addition for the first one and elimination for the second.
Original post by billybobs
This was really misleading, jumping straight into it I saw an amide link and put condensation. After looking at it more carefully I noticed nothing had been lost from the monomers, and also the question after stated it was 100% atom economy - so had to be addition.


But where does the hydrogen atom go from the OH groups of ethandiol? Crap. Another mark lost.

Original post by hayleyvictoria
Story of my life!


Chemistry is the bane of my life :tongue:
Reply 676
Avatar for Sujman
Sujman
1
Original post by C.JTop
addition 100% yield


How many marks was that
Reply 677
Avatar for manpyy
manpyy
Original post by Reina
I think there was a "is this addition or a condensation" question as well as a "classify this reaction question" but I can't remember what kind of reactants were involved :s-smilie:

I think I put addition for the first one and elimination for the second.



i got additions then elimination too :smile:
Original post by Reina
Did anyone divide Ka by three for the neutralisation of half the acid question?


I think I did something like that. Cause originally the salt/acid ratio was 1/1 so if half the acid reacts and gets turned into salt, you get 1.5/0.5 which equals 3? So Ka = [H+] x 3? pH came out as 4.2 or something I think, can't remember..
Original post by ells-13
Ye addition:smile: but my reason was no small molecule was eliminated, is that right?


Mmmm, possibly. I put no molecules are lost AND two smaller monomer units join together to form one large polymer.

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