Year 12s: what will be the first way you research your future options? >>

AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry

Scroll to see replies

Oh dear I can't do calculations to save my life

Can anyone guide me through this question 7D http://store.aqa.org.uk/qual/gce/pdf/AQA-CHEM5-W-QP-JUN10.PDF

I get upto working out the multiple of Fe and Cr2O72- to find the moles of Fe :s-smilie:

I would really appreciate it thanks.

MS http://store.aqa.org.uk/qual/gce/pdf/AQA-CHEM5-W-MS-JUN10.PDF

Reply 541

Sparkly-Star

Original post by InItToWinItGetIt?

Can I confirm, that cisplatin has two NH3 ligands right?

The AQA Nelson thornes book says it's NH2. :s-smilie:

Right I can't quite remember how this works but it is possible that it could be both, I remember my teacher saying something about it.

Reply 542

username555715

Original post by InItToWinItGetIt?

Can I confirm, that cisplatin has two NH3 ligands right?

The AQA Nelson thornes book says it's NH2. :s-smilie:

Yes it is definitely NH₃ as they have written further down the page (not that this excuses their mistake).

Reply 543

InItToWinItGetIt?

Original post by Sparkly-Star

Right I can't quite remember how this works but it is possible that it could be both, I remember my teacher saying something about it.

I don't even remember our teacher doing this lol.

Original post by ButterflyOfFreedom

Yes it is definitely NH₃ as they have written further down the page (not that this excuses their mistake).

Yeah that's what confused me and wikipedia said NH3 as well, so just wanted to double check. Thanks :smile:

Reply 544

ceeebs

Original post by al_habib

woow! thats hard core revision, am on 2006 now hope to finish by this afternoon the rest.

lol good luck :smile:

Reply 545

Mobs25

Original post by ButterflyOfFreedom

I may be wrong but I was under the impression that it is only synoptic for the topics in Unit 5. So they can ask anything we've previously learnt about on Inorganic, Energetics and Redox but not things like Organic as Unit 4 has a synoptic element for that.
Basically, any AS knowledge that was built upon in Unit 5, we can be asked questions on.

On the OLD specification there was an extra synoptic paper across the entire syllabus but now Units 4 and 5 are both "semi-synoptic" so to speak. Unit 5 cannot include Unit 4 knowledge because they can be taken in either order.

yeh this sounds about right to me... from the stuff ive seen in the previous papers they do ask a bit of synoptic questions but they are all related to the unit 5 chapters so nothing we wouldnt know really or nothing we would really need 2 speicifically remember... so i would then assume no unit 2 reactions etc would come up (well they might for the periodic chapter but thts it).

Reply 546

niharika.jha

Original post by NRican

I would really appreciate it thanks.

MS http://store.aqa.org.uk/qual/gce/pdf/AQA-CHEM5-W-MS-JUN10.PDF

Okay here goes...

(Fe2+ --> fe3+)x6
6e- + cr2o7 2- + 14H+ --> 2Cr2+ + 7H2O

Mol Cr2O7 2- is (0.100/1000)x23.50 = 2.37x10-3 mol
Ratio of Cr2O7 2- : fe2+ is 1:6
therefore mol of fe2+ is 6x2.37x10-3 = 0.0142 mol in 25cm3
Therefore in 250cm3 it is 0.0142x10 = 0.142 mol

Original mol in FeSO4.H2O is (10.0/277.9) = 0.036 mol
( mr of FeSO4.H2O is 277.9)

Therefore no of mol of fe oxidised is 0.036-0.0142 = 0.0218

So % oxidised is (0.0218/0.036)x100 = 60.56%

Hope that makes sense, I've just done it :smile:

Reply 547

cheekymon999

Hey all these posts about the synoptic stuff is confusing me :smile:

i asked my teacher about which synoptic stuff will come up and he said it will be CHEM2 - and he reckons it will be equilibrium stuff to go with the redox equilibria.
and obviously moles from CHEM1 is a given.

Anything else that people have been told might make an appearance?

Reply 548

strawberry_cake

Original post by Luke0011

Jan 11 and June 10 were both 73 for an A, 82 for A* :smile:

EDIT: Found Jan 10, 72 for an A :smile:

Aw thank you :biggrin:

Reply 549

InItToWinItGetIt?

Could someone explain the colour and electron transition thing to me. I'm confused, thanks :smile:

Reply 550

Wish I Could Change This

How on earth is everyone remembering the colour changes for complex ions?

Reply 551

Luke0011

Original post by InItToWinItGetIt?

Could someone explain the colour and electron transition thing to me. I'm confused, thanks :smile:

The outer electrons can absorb light, and get excited to a higher energy level.
They can absorb a certain frequency, so they could absorb blue, and so red light would be reflected off :smile:

That's all you need to know really i think!

Reply 552

usmana

could some one list all the colours and equations needed for trasition metals.

Reply 553

Tigerkins

Original post by NRican

I would really appreciate it thanks.

MS http://store.aqa.org.uk/qual/gce/pdf/AQA-CHEM5-W-MS-JUN10.PDF

If there is anything you don't understand just say. I got a little lazy on the rounding - But they allow anything from 60 to 61 anyway.
http://i54.tinypic.com/25tyidy.jpg

Reply 554

Sparkly-Star

Electrons jump from ground state to excited state don't forget!

Reply 555

YuDunno

My unhealthy obsession and me are very sidetracked.

:rolleyes:

IMG00643-20110602-1556.jpg414.6KB

Reply 556

Sheldon

Original post by InItToWinItGetIt?

Could someone explain the colour and electron transition thing to me. I'm confused, thanks :smile:

Electron will absorb Photons of light, the gain energy equal to the energy the photon had according to E=hf
when the electrons have this energy they enter an exited state where they move up the energy levels in the orbitals, after a given time they will de-excite fall down the levels and release photons of light, these will have a different frequency to the ones taken in as some energy was used going up the energy levels and as E-hf the frequency has to change. So in Transition metals they give out light in the visible part of the spectrum.
It all depends on what frequency of light is given out because each colour has its won frequency.

Reply 557

Arab_Empress

Original post by Luke0011

The outer electrons can absorb light, and get excited to a higher energy level.
They can absorb a certain frequency, so they could absorb blue, and so red light would be reflected off :smile:

That's all you need to know really i think!

Why does red light get reflected if blue light is absorbed?