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# AQA Chemistry C3 - Unofficial Mark Scheme

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How?
2. (Original post by Jakey236)
Anyone else get -217 for bond calculation?
i got -486.5
3. 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?
yahhhhh I got that !!!!!!!!!! how many marks was that 2 ????
5. (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
6. (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.
7. 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?
8. (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

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9. (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
10. Questions:
Natural source of methane: Natural gas (i don't really know if it's right)
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
11. (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.
12. I put calcium hydrogen-carbonate decomposes when heated to form calcium carbonate the scale etc would i get the marks still
13. (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
14. (Original post by Fr3dg)
How?
I wrote rubidium but I think the answer is fluorine
3444
17. (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 :/.
18. (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?
19. (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
20. 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

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