AQA GCSE Chemistry C2/C3 May 15th 2014 Watch

PAFCStan
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#481
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#481
I liked these papers generally. Only questions I didn't get were:
- the titration calculation for C3.
- the final question on the Haber process in C3. Guessed it was by fractional distillation even though that's alkanes from C1.
- the question about why silver is in water filters, again guessed because it kills microbes.

I think the two methods of water treatment for the first question were filtration to remove any solid particles, and treatment with chlorine to kill any microbes that may be in the water.
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Ben4
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(Original post by S.Ahmad)
Thats correct but the explanation is weak, the ink from the pen would have dissolved in the solvent, rising up the paper, therefore messing up the experiment.
Ok thanks

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chronicmusic
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#483
(Original post by WriterOfWrongs)
Hey where are these rumoured?

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A meeting between 21 chemistry teachers from across Kent (my great uncle is one of them!)
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S.Ahmad
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(Original post by PAFCStan)
I liked these papers generally. Only questions I didn't get were:
- the titration calculation for C3.
- the final question on the Haber process in C3. Guessed it was by fractional distillation even though that's alkanes from C1.
- the question about why silver is in water filters, again guessed because it kills microbes.

I think the two methods of water treatment for the first question were filtration to remove any solid particles, and treatment with chlorine to kill any microbes that may be in the water.
-The titration question was a simple case of substituting into a formula (Conc1 x vol1 = conc2 x vol2).
-Ammonia is solidified which is then collected and the unreacted Hydrogen and Nitrogen is sent off to the start where it is re-used.
-Silver prevents the growth of bacteria and also kills them.
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MUTTA
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(Original post by Hamzah313)
I think those are about right

wooow noo they have not been that high for years last few years shows patters that all the exams had similar grade boundires

which were
43 A*
36 A
27 B
21 C
13 D
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shanmancc
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#486
Hey, when are the official boundaries released?
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Hannah97
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(Original post by shanmancc)
Hey, when are the official boundaries released?
night before exam results i think
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just-wandering
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what did you guys get for the titration calculation in C3? I got 0.17 and this makes sense because:

The other substance had a volume of 25cm3 with a conc. of 0.2mol/dm3. The concentration of the substance looked for must have been less as this substance had a higher volume (26.8cm3)?
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interstitial
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(Original post by just-wandering)
what did you guys get for the titration calculation in C3? I got 0.17 and this makes sense because:

The other substance had a volume of 25cm3 with a conc. of 0.2mol/dm3. The concentration of the substance looked for must have been less as this substance had a higher volume (26.8cm3)?
I got this as well, we got the volumes the wrong way round (they sneakily put them in a weird order )

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james1202
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hey, you know on c2, what did people put for a) silica question about lower melting point,
b)how nanotubes are used as lubricants?
c)the question about conclusion of nanometeres on ph graph?
cheers guys
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just-wandering
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(Original post by majmuh24)
I got this as well, we got the volumes the wrong way round (they sneakily put them in a weird order )

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is it me or you just contradicted yourself there lol
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jomendo28
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#492
Those articles are about IGCSEs, not relevant for this exam as it's GCSE
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interstitial
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(Original post by just-wandering)
is it me or you just contradicted yourself there lol
I forgot to mention I got it wrong
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FS97
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(Original post by james1202)
hey, you know on c2, what did people put for a) silica question about lower melting point,
b)how nanotubes are used as lubricants?
c)the question about conclusion of nanometeres on ph graph?
cheers guys
a) Silicon Dioxide is mixed with other substances to make glass. I presumed the other substances simply cause the melting temperature to decrease (in comparison to Silicon Dioxide).

b) I think the layers of atoms can maybe slide over each other which is similar to graphite, and as they are nano-sized they have a very large surface area (I don't know how it relates to lubricants but I think that's what they're looking for).

c) The smaller the size of the particles, the greater the percentage of bacteria killed, and Bacteria Type 2 are slightly more resistant to the nano particles than Bacteria Type 1.

I don't know for sure if these are right but that's what I put from what I can remember
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just-wandering
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(Original post by FS97)
a) Silicon Dioxide is mixed with other substances to make glass. I presumed the other substances simply cause the melting temperature to decrease (in comparison to Silicon Dioxide).

b) I think the layers of atoms can maybe slide over each other which is similar to graphite, and as they are nano-sized they have a very large surface area (I don't know how it relates to lubricants but I think that's what they're looking for).

c) The smaller the size of the particles, the greater the percentage of bacteria killed, and Bacteria Type 2 are slightly more resistant to the nano particles than Bacteria Type 1.

I don't know for sure if these are right but that's what I put from what I can remember
a) I said it may increase the transparency of the glass as it stated in the question that the product already has a low melting temperature

b) Yeah, the atoms can slide over each other which means that it is slippery or there will be less friction between it and other surfaces

c) Wasn't it the bigger the size of particles?
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FS97
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(Original post by just-wandering)
a) I said it may increase the transparency of the glass as it stated in the question that the product already has a low melting temperature

b) Yeah, the atoms can slide over each other which means that it is slippery or there will be less friction between it and other surfaces

c) Wasn't it the bigger the size of particles?
It was definitely smaller, I can still picture the graph
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just-wandering
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(Original post by FS97)
It was definitely smaller, I can still picture the graph
so can I
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FS97
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(Original post by just-wandering)
so can I
Well it's commonly taught in Chemistry that increased surface areas increase the rates of reactions so it is fairly obvious to assume the smaller the nano particle, the more effective it was at killing bacteria
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just-wandering
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(Original post by FS97)
Well it's commonly taught in Chemistry that increased surface areas increase the rates of reactions so it is fairly obvious to assume the smaller the nano particle, the more effective it was at killing bacteria
Oh yes, damn I just realised. They were at 100% at ~8 particles then decreased from there on. Im sure I did get this correct in the exam though.
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james1202
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yeah, okay, i just wrote down a many legitimate sounding reasons i could think of for nanotubes, and I messed up the paper chromotography somehow, i didnt think; i thought the two dots that were at the bottom were the starting ones so i said a) fruit juice had one, cola had two b) cola had more, reckon ill pick up any marks at all for that? It was abstract one and two markers like the three mentioned , that made it so much harder than c3 for me
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