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AQA Chemistry C3 - Unofficial Mark Scheme

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Here is the bond energy once and for all:

ethanol + oxygen-->carbon dioxide + water
CH3CH2OH + 3O2 --> 2CO2 + 3H2O

on the left there are:
5*H-C bonds (each with an energy of 413) which totals 2065
1*C-C bonds at 347
1*C-O bonds at 358
1*O-H bonds at 467
3*O=O bonds (each with an energy of 495) which totals 1485
the total left hand side energy is the sum of these at 4722

on the right side there are:
4*C=O bonds (each with an energy of 799 [for CO2]) which totals 3196
6*O-H bonds (each with an energy of 467) which totals 2802
the total right hand side energy is the sum of these at 5998

4722-5998=-1276
it is left as a negative but a positive answer is fine at GCSE

but the next past said that the reaction was endothermic ah im confused now. everyone i asked also got 212J ah

Reply 241

srmed

Original post by Fractite

Scum is what I wrote.

Thank you! I wrote that too :smile:

Reply 242

Fractite

Original post by elifgecer

but the next past said that the reaction was endothermic ah im confused now. everyone i asked also got 212J ah

The next part said that the reaction was exothermic - it was a combustion reaction (which always gives out heat if you think about it lol.)

Reply 243

Roquebrune2014

Original post by Fr3dg

Spoiler

Ah hoping I'll get away with it!

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Reply 244

blueribbons99

Original post by Fractite

We had a specific heat capacity question (work out energy transferred) and the answer was 3444J.

Was that 100% still right because I still don't get it? I did 0.8x4.2x16.4 how many marks do U think for this?

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Reply 245

Fractite

Original post by blueribbons99

Was that 100% still right because I still don't get it? I did 0.8x4.2x16.4 how many marks do U think for this?

Posted from TSR Mobile

You used the correct formula and sort of the correct numbers. So, 2 marks (out of 3) maybe?

Reply 246

sarah400001

Arghhh I put the methane one as cows cause I couldn't think of anything 🙈🙈🙈🙈🙈

Reply 247

panic!intheexam

Guys I think if we got 212KJ then we were sitting further additional science not C3 like on this thread.

Reply 248

Fr3dg

Original post by elifgecer

but the next past said that the reaction was endothermic ah im confused now. everyone i asked also got 212J ah

first of all, obviously this reaction is exothermic, even though im 100% said it anyway in the test, its a combustion reaction, these are used to make fire, and heat, its pretty clear they are exothermic, since this heat is the energy that is released by the reaction.

Reply 249

greenapple10

Original post by Fr3dg

Spoiler

wait, were the two carbons given in the question, thats what i cant remember

Reply 250

Fr3dg

Original post by panic!intheexam

Guys I think if we got 212KJ then we were sitting further additional science not C3 like on this thread.

what was your question? as in the one on the further additional paper?

Reply 251

blueribbons99

Original post by Fractite

You used the correct formula and sort of the correct numbers. So, 2 marks (out of 3) maybe?

Okay hopefully!! Thank you(:

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Reply 252

panic!intheexam

I'm also pretty sure there was no specific heat capacity q in the further additional paper either?

Reply 253

Fractite

Original post by greenapple10

wait, were the two carbons given in the question, thats what i cant remember

yeah, they were already given.
we just had to fill out the functional group.

Reply 254

blueribbons99

Could anyone please upload a picture of what the energy diagram should look like?

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Reply 255

Fractite

What is the difference between further additional and triple anyway?

Reply 256

heather122333

Hey, for the methane question I knew methane was natural gas but rather than write 'natural gas', like most people here did, I wrote 'the atmosphere', do you think this is okay or wrong? I also wrote cow farms above it seeing a small cows produce methane.