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AQA CHEM5 A2 Chemistry - 19th June 2013

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So I lost most of the marks on the ratio question, I couldn't get the equations on the ethanol question, I somehow managed to get the Born-Haber cycle question wrong :colonhash:

, I lost the mark on why CO2 is released when recharging the cell as well as lots of others. But as there were also quite a few easy marks (17 marks on transition metal colours etc.), I think the grade boundaries will be quite high. :cry2:

Reply 2461

Pinkhead

Original post by marleyxd

For the transition metal complexes questions, did people write ionic or overall equations?

I wrote both for each reaction because it said write overall equations....

it said overall so i used the overall one.

Reply 2462

cat-lover

Original post by SpiggyTopes

What was the aldehyde question?

Ethanal got oxidised to ethanoic acid (I think). They gave us an equation then asked something about why cobalt catalyses the reaction (I think) and to write 2 equations.

Reply 2463

gizmokaka

Original post by Grauniad

For the reaction demonstrating why MgO was a basic oxide, why was it worth two marks? I hazarded MgO + 2HCl --> MgCl2 + H20, but I'm not sure how it amounts to two marks when the (arguably harder) one with NaOH and P4O10 was only worth 1.

Also, question 7 was probably the most tedious thing I've ever had to do in my life.

wasn't it the reaction with water? MgO + H20 ---> Mg(OH)2

Reply 2464

mulac1

I used CO3 2- etc... that will be fine it will never be penalised

Reply 2465

dizzy17

what was the equation and colours for the aluminium in excess ammonia?

Reply 2466

username1056419

Original post by Pinkhead

it said overall so i used the overall one.

I think it meant overall in that you were meant to add all the Ammonia in one go, for instance, rather than just taking a proton off each time. At least, I hope that's what it meant

Reply 2467

mulac1

Original post by gizmokaka

wasn't it the reaction with water? MgO + H20 ---> Mg(OH)2

yes I suppose you could have done that ... but it doesnt really react with water...
I reacted it with HCl to give MgCl2 and water

Reply 2468

Pinkhead

Original post by Grauniad

i thought it asked you to suggest an experiment to prove that the bonding is ionic?

Reply 2469

marleyxd

Original post by Pinkhead

it said overall so i used the overall one.

So for the HCl one, the one with Cu(H2O)6 would be
Cu(H20)6 + 4HCL --> Cu(Cl)4 + 6H2O + 4H+
??

Reply 2470

cat-lover

Original post by SpiggyTopes

I highly doubt that. XD I've probably dropped a lot more anyway but just can't remember. I do need an A* though because I got a C in chemistry unit 4 because I got food poisoning. :frown:

Reply 2471

Anshul91

Original post by gizmokaka

wasn't it the reaction with water? MgO + H20 ---> Mg(OH)2

No an acid and a base gives a salt and water

Reply 2472

extons

CH3CHO + Co3+ + H2O > Co2+ + CH3COOH + 2H+ + e-
2H+ + CH3CHO + O2 + Co2+ + e- > Co3+ + CH3COOH + H2O

Two catalytic equations.

Reply 2473

username1056419

Original post by gizmokaka

wasn't it the reaction with water? MgO + H20 ---> Mg(OH)2

Ooh, damn, it may well have been. Still don't understand why it was worth two marks though

Reply 2474

mulac1

do you think finding the total moles of Cl- using the moles of AgCl and finding the number of moles of Co2+ will get 2/5 on the last question?

Reply 2475

Pinkhead

Original post by Grauniad

I think it meant overall in that you were meant to add all the Ammonia in one go, for instance, rather than just taking a proton off each time. At least, I hope that's what it meant

yup, just add the 6NH3 in one go :smile:

Reply 2476

SpiggyTopes

Original post by Pinkhead

i thought it asked you to suggest an experiment to prove that the bonding is ionic?

You did, you melt it and if it conducts then it's ionic. :-)

Reply 2477

mulac1

Original post by extons

CH3CHO + Co3+ + H2O > Co2+ + CH3COOH + 2H+ + e-
2H+ + CH3CHO + O2 + Co2+ + e- > Co3+ + CH3COOH + H2O

Two catalytic equations.

oh no...that's definitely not what I got - I had one half equation where oxygen was reduced to water and then another where ethanal was oxidised to ethanoic acid. The waters then cancelled...