AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry

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That was a tough paper, I didn't quite remember what to put sometimes. =/

does anyone remember what they did for the moles calc at the end, I remember doing, I think I got the last part wrong (cant remember my answer)

Moles of cr
1:6 ratio to find moles of fe3+
mass/mr (used iron this is where I think I went wrong) to find moles of substance
moles of moles of solid-fe3+/moles of solid to find the percentage

(edited 12 years ago)

Reply 1302

m0man

Original post by i3kel

does anyone remember the equation for the moles calc at the end, I remember doing, I think I got the last part wrong

Moles of cr
1:6 ratio to find moles of fe3+
mass/mr (used iron this is where I think I went wrong) to find moles of substance
moles of moles of solid-fe3+/moles of solid to find the percentage

You didnt need to find the mole of substance, you just work out the mass of Fe by doing moles x Mr, then divide it by mass of substance x100= percentage

Reply 1303

Tigerkins

Really nice paper <3 Love you AQA :3

Reply 1304

Sparkly-Star

So you guys liked this paper? =/

Reply 1305

Naomiimoan

Original post by pts9

For that cell X question I put that I thought that it would be fuel cell but then in brackets bluffed about primary cells... are they completely different or could they be thought of as the same?

Why did the e.m.f. start to decrease with the first graph? I said that the products would increase and H20 may start to evaporate so the equilibrium may start to be established. Just couldn't articulate myself and had no idea what to say!

Overall I think it was an alright paper except those fuel cell questions, so I'm predicting 84 would be needed for an a*?

PIIPPPP

Reply 1306

Azzie_May

Original post by M | k e

Seemed a surprisingly alright paper to me :s and seemed really short weirdly.

Thats exactly what I though! Somehow I managed to finish the paper in an hour, it was a lot nicer than some of the past papers for sure :smile:

Reply 1307

508836

What did you guys get for the bond enthaply? what did you say for the lead-acid cell?

I seriously don't know how well/badly I did. Just have to wait till results day I guess.

Oh I confused (en) with (C2O2)2-. I must have been high. Oh well 4/5marks down.

Reply 1308

englishman129

I thought it was a fair paper... also enough hard marks to seperate a and a*. But nothing stupid like OCR.

Reply 1309

Spongy

I agree it was a nice paper.
However I feel there will be high grade boundaries, hope they are not significantly high though.

Reply 1310

Zakir

hey guys..

it was quite a fair paper tbh...for once!

i got 70%ish for the titration which i think is wrong because the ratio is 6:1...i did 8:1, how many marks do you think ill get?

for the first question (enthalpy of solution/hydration)...Was i right in changing the symbol for lattice formation because you have to dissociate the lattice and then put it in solution/water...

??

Reply 1311

jimmy303

I said that cell X was a standard cell since the emf didn't change (a high resistance voltmeter prevents the reaction from going so the equilibrium isn't approached and emf stays the same) but I was strongly tempted to put a hydrogen fuel cell...

Thought it was cheeky of them to ask for the reaction when the lead cell is recharged!

And only one colour of complex ions question :mad:

Other than those qualms I think it was ok.

edit: I also thought it was a tad cheeky of them to give us the reaction for the formation of 2 moles of ammonia then asked us to do questions based on the formation of one mole :eek:

(edited 12 years ago)

Reply 1312

lou12

Original post by Zakir

yes you were correct. what was your lattice enthalpy value. i got -51 (i think)

Reply 1313

magicalelf

Original post by mrppaulo

That was one which I really wasnt sure on :s-smilie:

I put:

Zn l Zn2+ ll H+ l AgO,Ag

However i have a feeling i should have included the water :s-smilie:

I put this also, spent ages trying to decide if i should include the H+ or not, argh!

Also the al2o3 one i waffled something about dissolving it in molten cryolite, applying a pd and if i current flows it contains ions, hopefully itll get me one mark :/

couldnt think what to put about why you cant recharge the cell, i put something about it breaking down the wall/casing and chemicals leaking out tho it was a complete guess :s-smilie:

overall a good paper i think but the redox cell question wasnt great and a few tricky questions also. hoping ive done enough for an A* but we'll see..

Reply 1314

M | k e

Original post by cleo101

for the question on the first page did people add the deltah lattice formation with hydration of the 2 elements added together

No I think you had to reverse the sign of the lattice of formation to get lattice of dissociation first, then add this value to the Ca2+ hydration and 2 times the F- hydration. Ended up with some small negative, like ~ -50 ish?

Reply 1315

lou12

Original post by jimmy303

Other than those qualms I think it was ok.

dammit. i put hydrogen fuel cell

Reply 1316

Shawman

Original post by lou12

dammit. i put hydrogen fuel cell

I'm pretty sure the answer was a fuel cell.

Reply 1317

subsist

Hey did people divide the ammonia equation by 2 cause it asked for one mole? :smile:

Reply 1318

mrppaulo

Original post by Zakir

Youll get the method marks so probably 1 mark for the ratio error and 1 mark for the actual answer.

And yes you needed the enthalyp of lattice dissociation so +ve value and you were given lattice of formation :smile:

so switch it round as you did :biggrin: