AQA Chemistry C3 - Unofficial Mark Scheme

Not sure I got crude oil.
Also 3444 is what I got.

Post your answers below, and we'll get an unofficial mark scheme!

Random answers:
Bond energies: -1276
Explain why: Energy needed making bonds was greater than energy released breaking bonds
Balance equation: 2 and 2 somewhere
Efficiency of Kettle: Hydrogencarbonate ions thermally decompose to carbonate, then react with calcium ions to product a precitipates of calcium carbonate (limescale). Limescale is a bad conductor of electricity - more energy needed to heat water
Hard water cleaner q: Calcium and magnesium ions replaced by sodium and hydrogen ions
Benefits of hard water: contains calcium which strengthens teeth and bones
Element that has low boiling point: F
What happens in the mixture of gases? Ammonia is liquified, then cooled - Nitrogen and Hydrogen are recycled
Specific heat capacity: 3444J
How is methane obtained: Cows (?)
Two boiling tubes: Tube A: fizzing because acid is dissolving calcium carbonate
Tube B: calcium carbonate produced, solution goes cloudy

again i was thinking fractional distillation, wish i wrote it down. Are you simply amazing at chemistry? Haha you have the answers for everything.

For the decomposition of HCO3 ions, I don't know why but I said it produced calcium carbonate AS WELL as magnesium carbonate, then I said these were precipitates (scale) which covered the heating element of the kettle - making it a poor conductor
Will I lose marks for saying magnesium carbonate?


Posted from TSR Mobile

For the energy change I divided 3444 by 0.8 and go 4305? ANYONE ELSE?

Will you lose a mark for saying 1623 rather than -1623?

Can you remember the question about methane? didn't it already say that its from natural gas and where did that come from? if you remember the question tell me pls

Shouldn't do - in papers both were allowed

I really screwed up C3. C1 and C2 went really well. Just hoping that they alongside my 24% on the ISA will help get me that A*. I messed up the bond calculation and added the oxygen etc. 😩 I'll get a mark for method but that it's. I also messed up the methane question and said that the methane stays a gas but the N2 and H2 condense! I may get a mark because I said that the H2 and N2 are reused. That table question at the start threw me as well.


Posted from TSR Mobile

it was apart from [something im unsure of] what is a source of methane?

so far, answers seem to be: fractional distilation of crude oil, decomposition, flactulance, and possible the hydrogenation of a methyl group but idek if you could do that.

Can you remember the question about methane? didn't it already say that its from natural gas and where did that come from? if you remember the question tell me pls

It was ammonia, not methane