Jan 2009 OCR AS CHEMISTRY HOW FAR HOW FAST

uksangho2000

dont think many people did this paper but if u did
post how u found it

the question im notsure about was bond enthalpy of f-f which i got 700

and the formation of CO i got 107 or 170 i think!
post ur replies!

Reply 1

.ACS.

19

I also got F-F to also be +700 kJ/mol. Can't remember for CO, though I think I put it as negative whatever the value was. :s-smilie:

I thought it was quite nice, especially the final large question on catalysis and what it does in a reaction. That was far too easy I thought. I did miss out on the three small 1/2 mark questions about acids and ionic equations because I totally forgot to go over them, though otherwise I felt it went well.

Reply 2

beee

i got F-F to be =700Kj/mol too! and i wasnt sure on it either, and i think i got 170, though i cant really remember if i got = or -. what did u right for the first question,? that the rate was increasin or decreasing?

Reply 3

.ACS.

19

I wrote that as time passed it decreased. It was fast to begin with (steep slope/gradient), and then decreased (more flat slope/gradient).

Reply 4

chud101

6

weyy i got -170 for the CO question !! lwking good so far

Reply 5

uksangho2000

OP

.ACS.

I wrote that as time passed it decreased. It was fast to begin with (steep slope/gradient), and then decreased (more flat slope/gradient).

oh s**t i just wrote 'increases'

i think all the writting questions were fairly straight forward, the calculations were a little confusing but overall it was alright.
Plus i know this question was so simple but what did u guys write about that on Numer 1, second question 'explain in terms of collision theory how the rate increases; i think

Reply 6

Toxic Tears

12

Overall it was quite a good paper,well it had to be the chains and rings one was sooo hard
I got 107 for the CO qu.

what did people put down for that HCl and HF question? I don't know if i wrote down the right equation for the NaCO3 + HF, couldnt work out what the products were :frown:

Reply 7

chud101

6

aw i got NaF2 + C02 + H20

Reply 8

beee

i put decreased too!! and for the second part i just explained why the graph was shaped like that using the collision theory. and i also got NaF2.
chud101 doing u want to do dentistry? me too!

Reply 9

chud101

6

beee

i put decreased too!! and for the second part i just explained why the graph was shaped like that using the collision theory. and i also got NaF2.
chud101 doing u want to do dentistry? me too!

Yeah dentistry all the way baby ! :wink:

Reply 10

borussia

i did this exam today and wrote in blue ink even though it said i had to use black on the front. what happens now? do i fail? will they mark it?

Reply 11

uksangho2000

OP

chud101

aw i got NaF2 + C02 + H20

hmm i dont think that is right u cant get NaF2
the equation was

Na2Co3 + 2HF ----> 2NaF + Co2 + h20

that is what i got

Reply 12

rogla

wooo! i got 700 for one answer, but -107 for the CO one.
if thought it was NaF not NaF2.... i put NaF, Co2 and H2o.
the paper was o.k.
did anybody else get for the temperature and pressure for high yeild and rate or reaction :
high temp
low pressure
high temp
high pressure
?

Reply 13

.ACS.

19

rogla

did anybody else get for the temperature and pressure for high yeild and rate or reaction :
high temp
low pressure
high temp
high pressure
?

Yup, I got that. :biggrin:

Reply 14

mogerman

borussia

i did this exam today and wrote in blue ink even though it said i had to use black on the front. what happens now? do i fail? will they mark it?

Read the paper first!...y messing up?

u be sooooo lucky if they mark it....soo lucky

i dont think they will, coz they mark it from the computer (most of the times)

Reply 15

Supersplodge

i thought it went pretty well! what did you guys get for the question regarding formation of HCL?

Reply 16

Supersplodge

this was how i worked out bond ethalpy of F-F :s-smilie:

H2 + F2 ----> 2HF delta H = -594kjmol-1 (was it?)
x + 436 = 2(568) - 594
x + 436 = 542
F-F = +106
436+106 = 542
542 - 1136 = -594kjmol-1

or

x + 436 = 2(568)
x + 436 = 1136
x = 700
is that how you guys worked it out?

also Na2CO3 + 2HF ---> 2NaF + CO2 + H2O

Reply 17

uksangho2000

OP

Supersplodge

this was how i worked out bond ethalpy of F-F :s-smilie:

H2 + F2 ----> 2HF delta H = -594kjmol-1 (was it?)
x + 436 = 2(568) - 594
x + 436 = 542
F-F = +106
436+106 = 542
542 - 1136 = -594kjmol-1

or

x + 436 = 2(568)
x + 436 = 1136
x = 700
is that how you guys worked it out?

also Na2CO3 + 2HF ---> 2NaF + CO2 + H2O

F-F Bond cannot be a Negative, where CL-CL bond is endothermic, surely F-F bond has to be endothermic as well, the second part is what i did and got 700

Reply 18

Supersplodge

uksangho2000

F-F Bond cannot be a Negative, where CL-CL bond is endothermic, surely F-F bond has to be endothermic as well, the second part is what i did and got 700

F-F = +106 (i think) :s-smilie:

Reply 19

ipatch

For the formation of carbon monoxide i got -107.

For the bond enthalpy of F-F i got 158 or 168..

andits 158 according to:
http://www.avogadro.co.uk/definitions/hbond.htm

Anyone else get this?

Jan 2009 OCR AS CHEMISTRY HOW FAR HOW FAST

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