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OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016)

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Original post by SGHD26716
I did this but accidentally for some reason put Ni instead of N. How many marks would be lost?


It was 2 marks so most likely 1, but if it was quite a small i the examiner might give you BoD as they mark quite quickly
It's scanned as well

so most likely 1/2 marks if the other bits are right
Reply 281
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S.G.
22
Original post by 2kk2
was the q value 4.something in kJ before working out the per mole??


I got 4.389 something along those lines
Original post by Jitesh
Are you sure? There's a very similar question to what came up on page 132 of the Oxford textbook (A-level edition)


Thinking about it, I think both ways can work since they gave both conc and vol... not sure
Reply 283
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87Mack
2
Original post by A Sajid
If Kc constant comes up im just going to walk out the exam I swear.:colonhash:


did you walk out then?
For the q=mct question would the mass have been 50cm3 because that was the mass of the solution they used?? I'm confused because some used 100cm3 and others 50cm3?? Also did anyone get the equilibrium question??? Because surely low temperatures wouldn't have produced a better percentage yield since the forward reaction was exothermic so low temp would shift equilibrium forward??? Also the high pressure would shift equilibrium to the right hand side since there were fewer molecules?? I just don't get that question at all
Original post by SGHD26716
I got 12 hydrogens and 6 oxygens and that goes 6 times for H2O. That what I did anyway.


Probably got the same, can't remember exactly the numbers
Original post by Fish40
I'm an idiot, didn't write a minus, so you divided your q by 0.075 mol and not 0.150mol, why?

Posted from TSR Mobile


I think they did divide it by 0.150molMaybe when working out q you used 50cm3 instead of 100cm3?
Can anyone make/link to an unofficial mark scheme? Thank you! :smile:
Reply 288
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S.G.
22
Original post by snickercell
For the q=mct question would the mass have been 50cm3 because that was the mass of the solution they used?? I'm confused because some used 100cm3 and others 50cm3?? Also did anyone get the equilibrium question??? Because surely low temperatures wouldn't have produced a better percentage yield since the forward reaction was exothermic so low temp would shift equilibrium forward??? Also the high pressure would shift equilibrium to the right hand side since there were fewer molecules?? I just don't get that question at all


I used 100 as they mixed the two solutions together
Reply 289
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87Mack
2
what did people get for the last question the 2 step process?
Original post by Jitesh
Was it not CrCl3.8H20 ? I think I remember getting 8 Oxygens

Might have been 6


100% sure it was CrCl3.8H20
What did you write for the Kc question?
Reply 292
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87Mack
2
Original post by A Sajid
100% sure it was CrCl3.8H20


nah it was 6H20
Reply 293
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2kk2
for the last question were you meant to add Hbr to the alkene so you get a haloalkane which formed the secondary alcohol - what were the regeants and how many marks would you lsoe if you missed out the regeants
Original post by 87Mack
what did people get for the last question the 2 step process?


I got Br2 to make a dibromo haloalkane and then NaOH(aq) to make the diol???
Original post by SP98
What was the concentration of KI?

3.3 i got
Original post by A Sajid
If Kc constant comes up im just going to walk out the exam I swear.:colonhash:


Unlucky man
How many significant figures or decimal places are you meant to use?
Original post by 2kk2
for the last question were you meant to add Hbr to the alkene so you get a haloalkane which formed the secondary alcohol - what were the regeants and how many marks would you lsoe if you missed out the regeants


It would be halogenation - just Br2 because you can't create -OH from the the H-C formed in nucleophilic addition. The reagents were Br2 and H2O as steam for the second part?


Posted from TSR Mobile
Original post by 2kk2
for the last question were you meant to add Hbr to the alkene so you get a haloalkane which formed the secondary alcohol - what were the regeants and how many marks would you lsoe if you missed out the regeants


Was it not a suitable halogen e.g. Br2 (electrophilic addition) then a suitable reagent like NaOH (nucleophilic substitution) ? as it asked for a two-way synthetic route rather than a mechanism for a direct route e.g. hydration with steam
It was 3 marks I think so maybe up to 2 marks without reagents

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