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

ocr a f325 revision thread

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Will you actually? XD I would take you up on that offer but I gotta wake up early because I have to go into school with my brother for his morning exam (my mum drives us). I woke up at 1 today. -_-"

Oh well, you need your sleep then. Make up for it in college. I'll be sleeping till nine. I remember when I had to do that in college, aaaah good times - it's got to be done.

Reply 2801

otrivine

Original post by kevloui

2FeO4 2- + 12H+ -----> 2Fe3+ + 6H20 + O2 ??

No but you are getting very close,

Reply 2802

_HabibaH_

Original post by AyshaK

moles = vol of gas/24 dm3

Yes that's one equation. There are three for moles though aren't they. Depending on what you're given, mass/molar mass or volume or concentration or combination of a few.

Reply 2803

eggfriedrice

Original post by _HabibaH_

(conjugate base/weak acid) x100 for percentage dissociation

What question would that come under? Buffer?

Reply 2804

JimmyA*

Good luck to you all, I have stupid general studies in the morning, so have to get up early :frown:

Reply 2805

Namod

Original post by otrivine

I am giving you a very hard demanding question,

Aqueous ferrate (VI) ions Fe04 2- decompose in the presence of hydrogen ions, forming Iron(III) ions, oxygen and water. Construct an ionic equation for this reaction

Fe6+ + 4O2- + 4H+ -> Fe3+ + O2 + 2H2O + e-

Reply 2806

AyshaK

Original post by otrivine

Cause in the book it stated that if a reaction is less than 0.4v a reaction cannot take place, and this is false info

Oh I got told when the standard electrode potential is negative then a reaction isn't feasible

Reply 2807

alltimeemilyxo

cell potentials;
the more positive voltage is the oxidising agent and so is reduced (?)
therefore does that reaction go forwards and the less positive one go backwards?

(edited 10 years ago)

Reply 2808

bluedate

Original post by _HabibaH_

Could you explain that a bit more please? I'd like to know what you're saying too!

On June 2010 paper Q6e)
Says C is a gas, at RTP C has mass of 1.17g

I want to know why they did 1.17 x 24
I thought the formula was n= v/24... :confused:

Reply 2809

paramountor

Original post by otrivine

The answer is:
4(Fe04)2- + 20H+ ----> 4Fe3+ + 3O2 + 10H20

Reply 2810

AyshaK

Original post by _HabibaH_

Yes that's one equation. There are three for moles though aren't they. Depending on what you're given, mass/molar mass or volume or concentration or combination of a few.

moles = mass / mr
moles = conc x vol

Reply 2811

_HabibaH_

Original post by eggfriedrice

What question would that come under? Buffer?

That came under Ka and acids in one of the papers.

Reply 2812

_sparks

Okay someone please answer this.
I cant figure this out.
Basically, dont we have to divide the moles of thiosulfate by 2 to get moles of Cu
The book got the moles of 2Cu^2+

Its page 223 of the OCR book. I attached the image too.

1.jpg280.9KB

Reply 2813

bluedate

Original post by JimmyA*

Good luck to you all, I have stupid general studies in the morning, so have to get up early :frown:

Same

Reply 2814

otrivine

Original post by Namod

Fe6+ + 4O2- + 4H+ -> Fe3+ + O2 + 2H2O + e-

No, where did Fe 6+ come from?

Reply 2815

otrivine

Original post by AyshaK

Oh I got told when the standard electrode potential is negative then a reaction isn't feasible

Like what do you mean sorry?

Reply 2816

Namod

Original post by otrivine

No, where did Fe 6+ come from?

Lol
then it must be:

Fe04 2- + 4H+ -> Fe3+ + O2 + 2H2O

Reply 2817

minthumbugs

Original post by alltimeemilyxo

cell potentials;
the more positive voltage is the oxidising agent and so is reduced (?)
therefore does that reaction go forwards and the less positive one go backwards?

imagine it as a number line, the more negative, the more to the left so the reaction goes backwards
the more positive, the more to the right so the reaction goes forwards

oxidising agents oxidise other things so are reduced themselves