The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

AQA GCSE Chemistry - C2 & C3 (14th May 2015)

Scroll to see replies

Reply 840
Avatar for annalg
annalg
2
Original post by LashiFire
I got 20 because it said the temperature change, so surely this would mean the highest change? And anyway, eventually the temperature would go back to room temp, which would mean (by the logic that you are using) that for every experiment the temperature change is 0.


Yes, I agree!
Original post by Positivedani
Urgh I totally messed up the last page! It all started with the amount where I put 30cm, then I didn't read the graph properly so put 38degrees as the overall change! That means I got the Q=mcdeltaT question wrong, and then for the last question I had no clue so wrote the neutralisation reaction will releade the same amount of energy -.- that page will bring my grade right down ergh!


i did that swell but won't you get the marks for error carried forward?
The best bit about C3 were the first 3 questions, they were nice and easy :smile:. Then it all kinda plopped D:
Original post by Nomes24
All your grade boundaries posts etc make you seem on your game and you got a lot of the answers right so far so don't doubt yourself!

Thanks, makes me feel a lot better :smile:


yo im tellin u postin graid bawnderees dont maik mee clvr u havnt seeen hao meni sili mistaiks i maid.

For example, I had no clue when I came to the question which asked how the scientist could find the concentration of barium sulfate (or was it barium hydroxide?). I don't like questions which give you loads of information about the method of the experiment, so I answered this last. All I could think of was that the yield of the reaction is never 100% so this affects the calculation of the concentration. I also put 'carbon dioxide' instead of hydrogen as the gas released in the reaction between sodium and ethanol, because I was most likely thinking of the reaction of ethanol and oxygen instead. There are also many two mark questions on ammonia, and I don't know whether what I've written qualifies for two marks or one mark.

I'm still remaining hopeful that the grade boundaries will be low.
Original post by Hannzz98
That's what I did, I wasn't sure if it was right


Posted from TSR Mobile


me too...i think it was right... One of my friends didnt even see the question erkkk
For the one about why you'd use a copper alloy in coins instead of pure copper, do you think that 'copper ores are running out so we need to preserve it as much as possible' would be alright?
Yeh; I emailed my teacher and asked and he said yes because thats why they ask for your working to be shown.
But to make things worse I used the wrong unit! So thats like 5 or 6 marks lost!
I don't know, I couldn't think of anything for that one :/. I put because copper is soft. I don't even know if copper is soft -_-
Original post by Palette
You don't actually know who I am.

:biggrin:

Anyway

Did you do this?

30+25= 55 cm^3

End temperature- initial temperature= overall temperature (energy) change in the experiment so 32-18= 14 C.

Specific heat capacity of water: 4.2 J/g/C

4.2*5.5*14= 3234 J?


To calculate the energy change wouldn't it be initial temp - end temp?
I know i got 55*20*4.2= 4620J...
Original post by Palette
You don't actually know who I am.

:biggrin:

Anyway

Did you do this?

30+25= 55 cm^3

End temperature- initial temperature= overall temperature (energy) change in the experiment so 32-18= 14 C.

Specific heat capacity of water: 4.2 J/g/C

4.2*5.5*14= 3234 J?


To calculate the energy change wouldn't it be initial temp - end temp?
I know i got 55*20*4.2= 4620J...:colondollar:
Did everyone talks bout collision theory in the b2 6 marker and say it reached its optimum temp after 0.7mol/cm3 of concentration because it was 35 degrees for the next three too? C2 was easy, c3 had some strange questions. I'm pretty sure that the overall temperature change was 14 degrees and the mass was 30g of HCL added to the 25g sodium sulfate or whatever it was so the equation was 55 x 14 x 4.2 (assuming the molecular mass was the same as joules as the question said) and the overall energy change was 3234 j or 32.34 kj
Original post by Jules12345
It was grams and carbon-12


is it not one twelfth Carbon 12 ??
guys what did you get for the empirical formula in the C2 paper? I got it wrong and mixed the two divisions at the very beginning up but i did the rest of the question working out right, would i get atleast a mark for that?
(edited 8 years ago)
Original post by bleeploop
is it not one twelfth Carbon 12 ??

No because the spec says carbon 12 I think
Original post by LaurenLovesMaths
For the one about why you'd use a copper alloy in coins instead of pure copper, do you think that 'copper ores are running out so we need to preserve it as much as possible' would be alright?

also copper is quite expensive so would be cheaper to use an alloy
Original post by kiwifruit99
To calculate the energy change wouldn't it be initial temp - end temp?
I know i got 55*20*4.2= 4620J...:colondollar:


Judge for yourself.
https://www.google.co.uk/search?q=overall+energy+increase&es_sm=93&source=lnms&tbm=isch&sa=X&ei=cLlUVavoD8iI7AbT34OIAg&ved=0CAgQ_AUoAg&biw=1366&bih=667#tbm=isch&q=overall+energy+change
Original post by Clintbarton
No because the spec says carbon 12 I think


I only put "carbon" for that. Do you think I'll get the mark?
I got Pb2O3 but I'm not sure if it's right :/

Posted from TSR Mobile
Original post by liverpoolfan7860
also copper is quite expensive so would be cheaper to use an alloy

It said do not refer to cost!!
Original post by LashiFire
I only put "carbon" for that. Do you think I'll get the mark?


No, because carbon has different isotopes which affect the mass, such as carbon-14. I can imagine the mark scheme will say 'carbon by itself insufficient'.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you