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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD

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Original post by TJB12345
Just going to throw out some numbers that are on my calculator and see if they ring a bell with anyone:

2.9 x10^-2
-1099
104
2.12
3.43
13.03
10.68

Anyone recognise these?


yes!!! haha good stuff
Original post by chelswaldx
Yeah I have a load of those numbers

Yes all of them!Apart from for 104 I gave it to 1 decimal place.
Original post by GillyTheGhillie
This word confused me for a second...


Machemguy is the one.
did anyone else find this exam very difficult ?
For the cr3+ as a reducing and oxidising agent question I wrote out the equations of cr3+ with ALL of the other half cells.I didn't realise only 1 and 2,and 6 and 7 react :/
Did anyone else do this?
Original post by Ula456
For the cr3+ as a reducing and oxidising agent question I wrote out the equations of cr3+ with ALL of the other half cells.I didn't realise only 1 and 2,and 6 and 7 react :/
Did anyone else do this?


Yes, but I think it's only 2 marks lost. No negative marking right?
Original post by MrZebraCookie
Yes, but I think it's only 2 marks lost. No negative marking right?

Phew ok thanks!I really hope so!I thought this paper went ok but I made so many mistakes! :/
Personally i thought this was easy peasy, i didn't even need the personal lessons daddy got me with the head of chemistry from Eaton. I reckon i could have done it after 6 bottles of champers and still have done well enough for an A*. I see there are a few people who didnt find it so easy which is a shame for them, but oh well i'll be laughing all the way to Cambridge.
some answers from prev pages and some that i remembered, if wrong, please correct:
[Cu(NH3)4(H20)2]2+
[CuCl4]2-
Draw the 2isomers out and trans. cis+ optical
Empirical F CuO10H4C4 with 2- charge
2.9 x10^-2 rate constant k
-1099hydation entalphy
104, Kc
2.12
3.43 pH
13.03
10.68
X= 4
CuCO3 ?
Starch solution, black/ blue to colourless
Linear
Ag=0 goes to +1, oxidised Ois 0 goes to -2, reduced
I2+ 2.5O2 arrow i2o5
6OH- + 3I2 arrow 3H2O + 5I- + IO3-
4I- + 2Cu2+ arrow I2 + 2CuI
Cu2+ is: 1s2 2s2 2p6 3s2 3p6 3d9.
Cu+ is: 1s2 2s2 2p6 3s2 3p6 3d10
Ligand subwith 4Cl?
Precipitationreaction with OH?
HNO2eqmarrow H+ + NO2-
Eqm movesright when OH added as makes water to replace H+
Eqm movesleft when H+ added, as makes HNO2

H2O2 + I- forms HIO + OH-
H+ + OH- forms H2O
HIO + I- forms I2 + OH- (given)
H+ + OH- forms H2O

or

H2O2 + I- forms IO- + H2O
IO- + H+ forms HIO
HIO + I- forms I2 + OH- (given in question)
OH- + H+ forms H2O

For the iodine question about adding AgNO3:
Ag + I -> AgI, [I-] decreases equilibrium 2 shifts left forming I- and I2(aq)
[I2(aq] increases equilibrium 1 shifts left forming I2(s)
Observations: Mixture of yellow (AgI) and grey black I2(s) precipitates is observed
-k.russell


The pH was given as 7 so I worked out the conc of h+ then divided kw by that to give OH-
OH- > H+ so I put alkaline
- maisum00

Emf= 0.60V

I2 is insoluble because it is non-polar and doesn't form hydrogen bonds
Bidentate ligand donates 2 lone pairs to form 2 coordinate bonds
Entropy increases because of more moles and solid becomes aqueous
Drawing a cell with platinum electrode and electrons/ions marked
-DrSerious

H+ not catalyst because not regenerated/
Has no impact on rate of reaction/
It is in the overall reaction equation

4Au + 8CN- + O2 + 2H20 = 4[Au(CN)2]- + 4OH-
(edited 7 years ago)
For anyone worrying about the last question, the answer was 7. I see a few people got 4, but they forgot to account for the hardness of the water. you have to add 3 becuase the water is hard.
(edited 7 years ago)
Original post by Charles Chester
For anyone worrying about the last question, the answer was 7. I see a few people got 4, but they forgot to account for the hardness of the water. you have to add 3 becuase the water is hard.

Do you think that water was trying to throw hands 👊👊💥✊?
Original post by GillyTheGhillie
You see, this is my problem, it IS their fault, if you don't know the specification like the back of your hand, and then some, you HAVE NOT done enough revision, none of the calculations were complicated, nothing was off-spec, none of the questions were worded badly, this wasn't some wet and oily lap in the reasonably priced car, this was perfect conditions, it was the choice of every student whether they wanted to drive the reliant robin (not revise) or a McLaren 675LT (revise).


Original post by GillyTheGhillie
Exactly. I guarantee there is not a single person here who came out of that exam feeling like they did awfully, who actually did enough revision.

It seems as though you've done so much 'revision' that your social skills are suffering. In what way are those posts helpful or constructive to people on here looking for answers/support? They serve absolutely no purpose other than to massage one's ego. I mean are you seriously that arrogant? Shocking... :facepalm:
Original post by Lion2121
I did this, you'd probs still get 2 I'd expect


i also did this :frown: threw me that there were more moles of salt than acid :frown:
Original post by alu4days
some answers from prev pages and some that i remembered, if wrong, please correct:
[Cu(NH3)4(H20)2]2+
[CuCl4]2-
Draw the 2isomers out and trans and optical
Empirical F (forgotit) with 2- charge
2.9 x10^-2 rate constant k
-1099hydation entalphy
104, Kc
2.12
3.43 pH
13.03
10.68
X= 4
CuCO3 ?
Starch solution, black/ blue to colourless
Linear
Ag=0 goes to +1, oxidised Ois 0 goes to -2, reduced
I2+ 2.5O2 arrow i2o5
6OH- + 3I2 arrow 3H2O + 5I- + IO3-
4I- + 2Cu2+ arrow I2 + 2CuI
Cu2+ is: 1s2 2s2 2p6 3s2 3p6 3d9.
Cu+ is: 1s2 2s2 2p6 3s2 3p6 4s13d10
Ligand subwith 4Cl?
Precipitationreaction with OH?
HNO2eqmarrow H+ + NO2-
Eqm movesright when OH added as makes water to replace H+
Eqm movesleft when H+ added, as makes HNO2


Empirical was CuC2H4O10 2-
For the isomers question it's one is trans the other is both cis and optical
For the electron config of Cu+ it's .....3p63d10 (the 4s electron is gone)
For the iodine question about adding AgNO3:
Ag + I -> AgI, [I-] decreases equilibrium 2 shifts left forming I- and I2(aq)
[I2(aq] increases equilibrium 1 shifts left forming I2(s)
Observations: Mixture of yellow (AgI) and grey black I2(s) precipitates is observed
and I thought that the question for the ionic equation was 2Cu2+ + 2I- -> 2Cu+ + I2, but I may well be wrong as I was doing this right at the end, was CuI a precipitate, if it is then you are right if it isn't I think I'm right
Nice work for putting those together thanks mate :smile:
THINK SOMEONE PUT THE EQUATION FOR THE CN- AG REACTION A FEW PAGES BACK IF YOU CAN TRACK THAT DOWN?
(edited 7 years ago)
what are 13.03 and 2.12 for?
Original post by k.russell
Empirical was CuC2H4O10 2-
For the isomers question it's one is trans the other is both cis and optical
For the electron config of Cu+ it's .....3p63d10 (the 4s electron is gone)
For the iodine question about adding AgNO3:
Ag + I -> AgI, [I-] decreases equilibrium 2 shifts left forming I- and I2(aq)
[I2(aq] increases equilibrium 1 shifts left forming I2(s)
Observations: Mixture of yellow (AgI) and grey black I2(s) precipitates is observed
and I thought that the question for the ionic equation was 2Cu2+ + 2I- -> 2Cu+ + I2, but I may well be wrong as I was doing this right at the end, was CuI a precipitate, if it is then you are right if it isn't I think I'm right
Nice work for putting those together thanks mate :smile:
THINK SOMEONE PUT THE EQUATION FOR THE CN- AG REACTION A FEW PAGES BACK IF YOU CAN TRACK THAT DOWN?


i think it said CuI was made and it was a precipitate and I added your changes/ observations and i'll try to find it
Original post by MrZebraCookie
Yes, but I think it's only 2 marks lost. No negative marking right?


Why 3 and 4 don't work ?


Posted from TSR Mobile
Original post by ShannonD_1697
Glad I'm not the only one...crying on the inside :smile:


Same :smile:
Original post by mamounaltayeb
Why 3 and 4 don't work ?


Posted from TSR Mobile


Cr3+ had to be on the left hand side
Original post by alu4days
i think it said CuI was made and it was a precipitate and I added your changes/ observations and i'll try to find it


you're right, CuI is insoluble in water dw
I was doing it right at the end cos I was doing the ionic equation for the question above (which asked for some other full equation) and realised my mistake with about 10 seconds left lol

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