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OCR Chemistry F322~ 4th June 2013~ AS Chemistry

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Original post by kingmango
Anyone got the jan 2013 paper?


opening post.
Reply 1761
Avatar for Saif95
Saif95
12
Could they ask about preparing an ester? Page 155 on OCR endorsed book
Original post by Saif95
Could they ask about preparing an ester? Page 155 on OCR endorsed book


all they'd ask is how to make one. so acid + alcohol and conditions of reflux and an acid catalyst.
guys anyone know the june 2009 grade boundaries?
Original post by Kitnimohabbathai
guys anyone know the june 2009 grade boundaries?


its at the end of the mark scheme for that paper
Reply 1765
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Pataiiii
Original post by Anonymous1717
Thanks!

No problem.
Reply 1766
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cab1094
1
Predictions anyone? 😊


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I don't know if this is really obvious but when you do the Q=mcat equation how do you know if you get it in j or kj? also, can it ever be negative?
Reply 1768
Avatar for rosie66
rosie66
Help needed! :smile:
H(2) + Cl(2) --> Cl(2) enthalpy change= -418 kJ mol^(-1)

bond enthalpy for H-H is +436 and for Cl-Cl is +243

work out the bond enthalpy for H-Cl?
Original post by chasdfghjk
I don't know if this is really obvious but when you do the Q=mcat equation how do you know if you get it in j or kj? also, can it ever be negative?


It is in joules as the units of the heat capacity of water is in J g-1 K-1. It will not be negative, you need to decide if it is negative or not based on whether the temperatuere increases or decreases.
Original post by chasdfghjk
I don't know if this is really obvious but when you do the Q=mcat equation how do you know if you get it in j or kj? also, can it ever be negative?


the units for q are joules, therefore your answer will automatically be in joules. they always ask for it in kj so divide your answer by 1000.
you cant have a negative energy, you can only have negative enthalpy changes, theyre different things so only give a negative sign when it asks for an enthalpy change (only if the temperatures gone up though)
Reply 1771
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tanja55
1
Original post by chasdfghjk
I don't know if this is really obvious but when you do the Q=mcat equation how do you know if you get it in j or kj? also, can it ever be negative?


no it will never be negative for the q=mcat because you can't have a negative mass value and when you divide the q=mcat by 1000 you always get it in KJ when you dont divide it by 1000 you will always get in J

Hope this helped :biggrin:
Reply 1772
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WaseemB
Original post by ChestnutHero
What mark out of 100 do you think you need to get 150 UMS :smile: ?


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94/100 usually :smile:

https://www.whatdotheyknow.com/request/raw_mark_for_100ums_in_biology_a?unfold=1


may get higher as students are more prepared apparently due to more past papers available..
Original post by rosie66
Help needed! :smile:
H(2) + Cl(2) --> Cl(2) enthalpy change= -418 kJ mol^(-1)

bond enthalpy for H-H is +436 and for Cl-Cl is +243

work out the bond enthalpy for H-Cl?



? The enthalpy change for H2 + CL2 -> CL2 is 0 kJ mol-1
Reply 1774
Avatar for tanja55
tanja55
1
Original post by rosie66
Help needed! :smile:
H(2) + Cl(2) --> Cl(2) enthalpy change= -418 kJ mol^(-1)

bond enthalpy for H-H is +436 and for Cl-Cl is +243

work out the bond enthalpy for H-Cl?



are you sure you copied the equation down write?
Reply 1775
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tanja55
1
how many UMS would you get with 95 raw mars?
Reply 1776
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rosie66
Original post by tanja55
are you sure you copied the equation down write?


yeah sorry.... H(2) + Cl(2) --> 2HCl

sorry
Original post by tanja55
how many UMS would you get with 95 raw mars?

100 usually
Reply 1778
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Namod
10
Original post by tanja55
are you sure you copied the equation down write?


your english is killing me
Reply 1779
Avatar for Tejmasta
Tejmasta
Doing q2 ii of june 11 paper

I said heat under reflux as the reaction conditions, but mark scheme says:

distil --> Guidance: Reflux CONs distil mark

what does the CON mean?

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