AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry Watch

LimeTree.
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#21
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#21
(Original post by Miss Purple)
Who else has this for their last exam?? 25th June is going to be an epic day B)
Its the 24th. But.. yes
Gotta love good old chemistry haha
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animal*nature
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#22
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Could someone please explain to me how you do the titration question on page 228 question 2 in the nelson thornes book.
Thanks in advance!
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MoMatrix
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(Original post by animal*nature)
Could someone please explain to me how you do the titration question on page 228 question 2 in the nelson thornes book.
Thanks in advance!
I think you balance the equation chemically there should be a 5:1 ratio haven't done the question so calculate no of moles of Fe then use the n=m/Mr.
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M.A.
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ARGH, this module is ridiculous! But I've just about tackled all the transition metal colours etc, i think...

Anyway, anyone know whether we actually have to know about using thiosulfate in redox titrations (reducing iodine etc..)??
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Miss Purple
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how's revision going guys??
got my ISA result.. 1 measly mark off an A
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animal*nature
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Hey peeps on page 212 in the nelson thornes book how do u work out question 1biii ? I don't really understand what the Mark scheme is saying ! Thanks
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rrelish
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(Original post by animal*nature)
Hey peeps on page 212 in the nelson thornes book how do u work out question 1biii ? I don't really understand what the Mark scheme is saying ! Thanks
Hey, Im not too sure - when i asked my teacher he said we didnt need to know this, as its from the old syllabus....but
If you write out the overall equation, i think by decreasing the Fe3+, it would cause the equilibrium to shift to the right and increase the emf of the cell?
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rrelish
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#28
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Has anyone done chem 4 june 2010 - the last last question 7(d)
Why, at the end do you minus your answer from the original moles?
can you not just divide the answer you get by the original moles?

Thank you
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undertaker1
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#29
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hey can someone help me with the equations for reactions of inorganic compounds in aqueous solution:

are we suppose to learn the overall equations or step by step equations or both.

e.g. for CU2+ with the base=ammonia do we use OH or NH3 to produce CU(OH)2(H2O)4

and to get CU(NH3)4(H2O)2 what is the overall equation

really confused guys sorry for the grammer

any help very much appreciated

and has anyone got a table/chart for every single equation for transition metals because the books are useless.

thank you
Last edited by undertaker1; 7 years ago
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rrelish
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(Original post by undertaker1)
hey can someone help me with the equations for reactions of inorganic compounds in aqueous solution:

are we suppose to learn the overall equations or step by step equations or both.

e.g. for CU2+ with the base=ammonia do we use OH or NH3 to produce CU(OH)2(H2O)4

and to get CU(NH3)4(H2O)2 what is the overall equation

really confused guys sorry for the grammer

any help very much appreciated

and has anyone got a table/chart for every single equation for transition metals because the books are useless.

thank you

HEY!!!

You should learn the steps as well as the overall equation

I was also confused if when you add dilute ammonia, should you write OH- or NH3? I saw in the mark scheme that you shoud use NH3, so you would get for Cu:

[Cu(h20)6]2+ + 2NH3 -----> Cu(h20)4(OH)2 (s) + 2NH4+

then when ammonia is added in excess:

Cu(h20)4(OH)2 + 4NH3 -----> [Cu(NH3)4(h20)2]2+ + 2h20 + 2OH-

The overall is (with conc ammonia):
[Cu(h20)6]2+ + 4NH3 -----> [Cu(NH3)4(h20)2]2+ + 4h20


I made a big table with the equations and colours - got them all from the AQA book, some you have to work out from the ones they've given you.

Hope my explaining helped!
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Y.D
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I know this paper is synoptic, so I'm anticipating the 1 mark questions on bond angles, intermoleculer forces etc... can they ask us something like proton nmr, from unit4 that's not a general thing we have learnt in every unit
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jimmy303
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#32
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(Original post by Y.D)
I know this paper is synoptic, so I'm anticipating the 1 mark questions on bond angles, intermoleculer forces etc... can they ask us something like proton nmr, from unit4 that's not a general thing we have learnt in every unit
It says on the specification under the Synoptic heading that questions that test synopticity will be based on units one and two only (i.e. AS content) since it's common for people to do unit 5 before or at the same time as unit 4.

Also you should know that unit 4 exams test synopticity, you just might not have noticed it I wouldn't worry about this aspect of the exam so much; as long as you learnt the content during AS you shouldn't even notice that the questions you're being asked aren't part of unit 5.
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magicalelf
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The worst part I think with the synoptic questions is the AS periodicity stuff, and any extraction of metals! Seem to have completely forgot about all that so need to go over it.. rest synoptic-wise should hopefully be alright!
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Y.D
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#34
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(Original post by jimmy303)
It says on the specification under the Synoptic heading that questions that test synopticity will be based on units one and two only (i.e. AS content) since it's common for people to do unit 5 before or at the same time as unit 4.

Also you should know that unit 4 exams test synopticity, you just might not have noticed it I wouldn't worry about this aspect of the exam so much; as long as you learnt the content during AS you shouldn't even notice that the questions you're being asked aren't part of unit 5.
Thanks, i don't think the AS synoptic stuff will be too bad, I guess this spec is still relatively new so AQA could pull out some new tricks, as they do
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jimmy303
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(Original post by Y.D)
Thanks, i don't think the AS synoptic stuff will be too bad, I guess this spec is still relatively new so AQA could pull out some new tricks, as they do
AQA are renowned for doing that it's true :mad:

Don't forget about the past papers from the old spec though. Apart from the odd question (which you'll be able to recognise as part of unit 4) they're really useful as preparation for the exam as the syllabus is almost identical to the current one
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ben10
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#36
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does anyone know what the reactions are when hydrogen peroxide is added to cobolt " suplate under alkaline conditions
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jimmy303
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(Original post by ben10)
does anyone know what the reactions are when hydrogen peroxide is added to cobolt " suplate under alkaline conditions
[Co(H2O)6]2+ --> [Co(H2O)6]3+ + e-
H2O2 + 2e- --> 2OH-

Therefore:
2[Co(H2O)6]2+ + H2O2--> 2[Co(H2O)6]3+ + 2OH-
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ben10
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#38
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(Original post by jimmy303)
[Co(H2O)6]2+ --> [Co(H2O)6]3+ + e-
H2O2 + 2e- --> 2OH-

Therefore:
2[Co(H2O)6]2+ + H2O2--> 2[Co(H2O)6]3+ + 2OH-
cheers
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Madderroo
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#39
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does anyone have the mark scheme for AQA Chem 5 Feb 2010?
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Spongy
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hi, can someone help with this question:

its the february 2010 paper, question 8(c):

A chemical company has a waste tank of volume 25 000dm3. The tank is full of
phosphoric acid (H3PO4) solution formed by adding some unwanted phosphorus(V)
oxide to water in the tank.
A 25.0cm3 sample of this solution required 21.2cm3 of 0.500 mol dm–3 sodium
hydroxide solution for complete reaction.
Calculate the mass, in kg, of phosphorus(V) oxide that must have been added to the
water in the waste tank.


this is what the mark scheme says:

Moles NaOH = 0.0212 × 0.5 = 0.0106
Moles of H3PO4 = 1/3 moles of NaOH (= 0.00353)
Moles of P in 25000 l = 0.00353 × 106 = 3.53× 103
Moles of P4O10 = 3.53 × 103/4
Mass of P4O10 = 3.53 × 103/4 × 284 = 0.251 × 106 g
= 251 kg

I dont get how they worked it out . I undestand the first line of the mark scheme and that is it.
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