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

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Original post by BioStudentx
It was bae.

Finished with 30 mins to spare, and yes I got 4H2O. Grade boundaries will be disgustingly high though. Similar to last year, maybe 1 higher.


you are literally so annoying, me and 3 others from my college that are going to oxbridge said that it was definitely harder than last years and a lot of people found it hard. don't be so patronising to the other people you snob
Original post by BioStudentx
Acidic. Position of eqbm shifts to right at higher temperature, as it's endothermic.

The "actual pH" was 6.03


It asked whether a ph of 7 is acidic/alkaline at 60 degrees, so using the new Kw, you get that the concentration of oh- is larger than the conc of H+ so it is alkaline
Original post by biostudentx
hio + oh- for step 1, instead of what you got.


h2o2 + i- > hoi + oh-
hoi + i- > i2 + oh-
given
2oh- + 2h+ > 2h2o
Everything correct except for the first number, it said 2 sf so 0.029 it also said standard from so 2.9x10-2 I'm afraid probs -1 mark tho so not too much to worry about, didn't spot that one till second time round
Original post by BioStudentx
pH of the buffer was 3. something. Anyone who wrote anything else got it wrong.


Original post by EricPiphany
Some answers I scribbled down:

0.0285
104.2
2.12
3.43
10.76
4

Hopefully I did well enough for an A overall. Chemistry is now over. Hell yeah!

Yes bois

I think I lost a mark on the first one for wrong s.f :/

And the buffer one, you were simply adding x moles NO2-...
Original post by BioStudentx
Acidic. Position of eqbm shifts to right at higher temperature, as it's endothermic.

The "actual pH" was 6.03


im sure it was Alkaline...Or did I make a *****y error-.-

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Original post by sophiewei
I put alkali. Because i worked out neutral ph as 6.5 so 7 is greater than 6.5 therefor alkali.


i did it by finding out the concentration of (h+) and the concentration of (oh-) and since the concentration of (oh-) was most than (h+), this shows that it was in fact alkaline, but few others did it your way too so i assume your method might be correct
Original post by tomlam
Anyone think that exam was bae?

(oh, except that question at the bottom of the second to last page)

Anyone get 4H2O for the last Question?
Anyone finish with 45 minutes to spare?


Im sure when i say this. I speak on the behalf of majority of students that this exam was not "bae" .. but paper was adequate.
Original post by HFancy1997
Everything correct except for the first number, it said 2 sf so 0.029

Posted from TSR Mobile


Didn't it also say in standard form? I put 2.9 X 10^-2
It was the same shape as water, i swear thats non-linear or bent shaped
Original post by suibster
the shape is linear
Reply 3410
Avatar for Jsey
Jsey
Original post by cr7alwayz
Can anyone explain how x=4 for the last question if you remember your working out.


You work backwards through the titration to find the moles of Cu2+. Then you multiply the moles of Cu2+ by the molecular mass of Cu(HCOO)2 to find the mass in grams. Then you subtract this value from the grams they gave you in the question. Then you use the remaining grams to find the moles of water. Using moles equals mass over molar mass. Then lastly you divide the moles of water by the moles of the Cu2+ to get the molar ratio.
(edited 7 years ago)
Original post by HFancy1997
im sure it was Alkaline...



Posted from TSR Mobile

yeah it was alkaline since more contraption of oh- ions than h+ so acidic is wrong I'm afraid
Have a feeling grade boundaries could be 67-73 for an A, 75-81 for A*.
Original post by Fmathslad
you are literally so annoying, me and 3 others from my college that are going to oxbridge said that it was definitely harder than last years and a lot of people found it hard. don't be so patronising to the other people you snob


Agreed! Definitely not harder than last years and won't have higher UMS I think it will be around 90->82>76... -> 150>135>120
X=4 q was bare cute
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

Anyone else?
Reply 3416
Avatar for four4
four4
2
Which question was the pH 2.12 for?
For the equilibrium question I put: I- reacts with Ag to form agI (yellow ppt), therefore the position of equilibrium will shift to the left to restore I- conc. As a result, more aqueous iodine was formed so the position of equilibrium of 1 will also shift to the left, therefore more grey/black solid iodine is formed. For the electrochemistry question I needed up with two equations. The oxidising agent one where Cr+3 reacts with AL and the reducing agent one where Cr+3 reacts with feO4- or something. Anyone else?
I agree with u man, i think i grabbed the A mark but being honest that paper was relatively harder than last years, GB for last year was 79 for an A. if you find the paper easy have the common decency to not brag and think about others.
Original post by Fmathslad
you are literally so annoying, me and 3 others from my college that are going to oxbridge said that it was definitely harder than last years and a lot of people found it hard. don't be so patronising to the other people you snob
Original post by cr7alwayz
Can anyone explain how x=4 for the last question if you remember your working out.

I worked out the moles using the info they gave.
Divided it by 2 because of the mole ratio.
Then multiplied by 2 because of the mole ratio.
Multiplied that by 10 because it was in 250cm3.
Worked out the mr by 2.226 divided by the moles I worked out.
Subtracted the mr of cu(choo)2 from the mr calculated.
Then divided the answer by 18, I got 3.5, so 4=X

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