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AQA Chemistry C3 - Unofficial Mark Scheme

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Reply 60
Original post by adam_jeffries
The answer is rubidium


How?
Reply 61
Original post by Jakey236
Anyone else get -217 for bond calculation?


i got -486.5
On the specific heat capacity question I think I got an answer of around 55.104? Didn't you have to do 0.8 x 4.2 x (38.4-22.0) since that was the temperature change?
Original post by adam_jeffries
3444 is the right answer


yahhhhh I got that !!!!!!!!!! how many marks was that 2 ????
Reply 64
Original post by Roquebrune2014
For bond energies I am 100% sure it should be (-)1,276. I wrote out all the bonds underneath next to their bond energies, added up each side of the reaction and checked the numbers 3 times (I finished quite early so thought I'd count up each side again)


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that's what I got :smile:
Reply 65
Original post by ThomasSidney1
On the specific heat capacity question I think I got an answer of around 55.104? Didn't you have to do 0.8 x 4.2 x (38.4-22.0) since that was the temperature change?


Not 0.8, it was 50. It was meant ot be mas of water heated not mass of alcohol.
For the specific heat capacity, didn't it ask for the energy of the alcohol, so you used the mass of the alcohol not the water?
Reply 67
Original post by ThomasSidney1
On the specific heat capacity question I think I got an answer of around 55.104? Didn't you have to do 0.8 x 4.2 x (38.4-22.0) since that was the temperature change?


I got that but I think it's wrong :frown:


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Reply 68
Original post by ThomasSidney1
On the specific heat capacity question I think I got an answer of around 55.104? Didn't you have to do 0.8 x 4.2 x (38.4-22.0) since that was the temperature change?


It is 50x4.2x16.4, if they asked you to find energy released per gram, you would then divide this by 0.8, but they didn't
Reply 69
Questions:
Natural source of methane: Natural gas (i don't really know if it's right)
Elements with lowest boiling point: Fluorine (had a look on Google)
2 observations that you will see in the test tubes for the reaction of sodium carbonate and ethanoic acid: effervescence in the 1st tube, the presence of carbon dioxide gas causes limewater to turn cloudy in 2nd test tube.
Combustion of ethanol: C2H50H + 302 -> 2CO2 + 3H20
Reply 70
Original post by Antediluvian
For the specific heat capacity, didn't it ask for the energy of the alcohol, so you used the mass of the alcohol not the water?


Sadly not, when doing a calorimetry test, you want to see how well the burning of the fuel will heat the water, which is why you use the volume and specific heat capacity of the water, and the temperature change experienced by the water.
I put calcium hydrogen-carbonate decomposes when heated to form calcium carbonate the scale etc would i get the marks still
Reply 72
Original post by Fr3dg
I think 3



Thanks! I believe you get 1 mark for the Correct temperature (Delta Theta)
1 mark for rearranging the equation
1 mark for the right answer
Reply 73
Original post by Fr3dg
How?


I wrote rubidium but I think the answer is fluorine :frown:
Reply 74
Original post by adam_jeffries
That answer is right


which ANSWER? 4305 or 3444?
Original post by Sadxa
which ANSWER? 4305 or 3444?


3444
Original post by Fr3dg
Sadly not, when doing a calorimetry test, you want to see how well the burning of the fuel will heat the water, which is why you use the volume and specific heat capacity of the water, and the temperature change experienced by the water.


Thanks, I am such an idiot :/.
Reply 77
Original post by Fr3dg
Sadly not, when doing a calorimetry test, you want to see how well the burning of the fuel will heat the water, which is why you use the volume and specific heat capacity of the water, and the temperature change experienced by the water.



So what is the answer? 4305 or 3444?
Reply 78
Original post by Francis197
I put calcium hydrogen-carbonate decomposes when heated to form calcium carbonate the scale etc would i get the marks still


If u talked about the effect on thermal conduction of the kettle, meaning more energy was required to heat the water to the same temperature as well, then I'm sure you would've got the marks
i misread the units and put -1.276 becos i divided by 1000 at the end; will i lose only 1 mark or all 3?
Original post by row1409
that's what I got :smile:

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