[Matthew692692]

Is ligand exchange the same as ligand substitution?


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[shuaib786]

(Original post by Matthew692692)
Is ligand exchange the same as ligand substitution?


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Yeah it is.

[Josh1993]

(Original post by danielpickwick)
The very last part to question 8b) is

O2 + 4Co2+ + 4H+ -------> 2H2O + 4Co3+
2SO32- + 2H2O + 4Co3+ ------> 2SO42- + 4H+ + 4Co2+

Thank you.

[Matthew692692]

(Original post by shuaib786)
Yeah it is.

YES ONE MARK!!!!


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[Josh1993]

Would anyone beneft with mark allocations
?

[Matthew692692]

(Original post by Josh1993)
Would anyone beneft with mark allocations
?

It would be useful if they were on the markscheme

[stomakow]

(Original post by Josh1993)
I suffer really bad exam pressure , looking back i lost around the same as you for making silly mistakes but ican assure the answers I have put are correct(excluding typing errors)

Tbh the mistakes i made would not have mattered if i had time to go through the paper again. But i didnt. I barely finished it. Normally id have a lot of time left to check through. Not this time.

[Josh1993]

(Original post by Matthew692692)
It would be useful if they were on the markscheme

Okey dokey .
Ill may not respond then , im not being rude

[uxa595]

(Original post by Josh1993)
decided to crrate a mark scheme of sorts for the much contraversial AQA chem 5 exam.

1. a) It spontaneously ignites in air.
b)P2O5 is the emperical formula.
c)Larger molecule, stronger VDW forces.
d) P4O10 + 6H20 ----------------> 4H3PO4 PH approx 1
e)2H3PO4 + 3MgO -----------> Mg3(PO4)2 + 3H20
f) Only forms a weakly alkaline solution (approx 10)
e) forms a strong alkaline solution

2 a) ΔG = ΔH-TΔS
b) 0.1 KJmol^-1k^-1 ΔS
c) The point at which the reaction becomes feasible.
d) phase change.

3 a) The enthalpy change when one mol of gaseous anions are formed from one mol of gaseous atoms.
b) Greater charge density( smaller atom, less shielding etc....)
c) stronger forces of attraction between lone pair on water and the more highly electonegative flourine.Hydrogen bonding
d)950 kJmol^-1
e) solid -----> aqeous more disorder.
f) Enthalpy change is neagtive and the entropy change is posotive.

4) ΔH = -56 KJmol^-1
b) ΔS = -70.5 JK^-1mol^-1
c) T = 794 K
d) Heat is too high to be feasible.
e) N2 + O2 -----> 2NO
f) phase is the same, moles are equal. ΔH is constant.

5) electron acceptor.
b) Cd(OH)2 lowest value.
c) 1.5 V
d) 2MnO2 + 2H2O + Zn --------> 2MnO(OH) +2OH- +Zn2+
e) allow ionic current to flow through the separator. (stop short circuit.)
f) conduct an electic current.
g) conversion into Zn2+
h) +3, 2NiO(OH) + 2H20 +Cd ---------> 2Ni(OH)2 + Cd(OH)2
I) Reduces landfill.
j) C2H5OH + 3O2 -----------> 2CO2 + 3H2O
K) C2H5OH + 3H2O ---------> 2CO2 +12H+ + 12e-
l) 0.23V
l) equal number of mols in photosynthesis and fermentation.( 6:6)

6) co-ordinate bond
b) water acts as a lewis base, donates a lone pair of electrons.
c)180 degrees
d) The much talkeD about question. Combine the half equation by * the top one by 3 and the others by 5.
3MnO4- +24H+ +5Fe(C2O4) ------> 3Mn2+ +12H2O + 5Fe3+ +10C02
e) 94%/93.6 ( The ratios given are out of order I personally think they should discard this question)


7) orange ----> green ---> blue
Cr2O72- Cr3+ Cr2+
Cr2O72- +14H+ +3Zn -----------> 2Cr3+ +7H2O +3Zn2+
2Cr3+ + Zn -------> 2Cr2+ + Zn2+

b) green sol'n/violet ------> green ppt ---------> green sol'n

[Cr(H20)6]3+ + 3OH- -------------> [Cr(H20)3(OH)3] + 3H2O
[Cr(H20)3(OH)3] + 3OH- ------------> [Cr(OH)6]3- + 3H20

C) ligand substitution ( change in charge) change in ligand d-d transition different e=hf therefore diffrent wavelenghts reflectedetc...

d) oxidised in air(reference to potential values)
CrC03
Cr(OH)3 water CO2
More acidic (charge density polarising O , Draws electron density from O-H) etc...

8) a) CONC NH3

[Co(H20)6]2+ + 6NH3 -----------> [Co(NH3)6]2+ + 6H2O

O2 / H2O2

4[Co(NH3)6]2+ + O2 + 2H2O ---------> 4[Co(NH3)6]3+ +4OH-
2[Co(NH3)6]2+ + H2O2 -----------> 2[Co(NH3)6]3+ +2OH-

CONC HCL

[Co(H20)6]2+ + 4Cl- --------------> [Co(Cl)4]2- +6H20

Sodium carbonate
[Co(H2O)6]2+ +CO32- --------> CoCO3 +6H20

B)

2SO32- + O2 -------> 2SO42-

O2 + 4Co2+ + 4H+ -------> 2H2O + 4Co3+
2SO32- + 2H2O + 4Co3+ ------> 2SO42- + 4H+ + 4Co2+

lower energy pathway , lower activation energy.

I dont know this last bit , feel free to add your two pennies worth.
rep appreciated if you feel this has helped you.

You think i can get a mark for saying it's a acid-base reaction for q1 after the balancing equation thing?

[thenumber2goose]

(Original post by Josh1993)
7)
b) Ruby soln ------> green ppt ---------> green sol'n

[Cr(H20)6]3+ + 3OH- -------------> [Cr(H20)3(OH)3] + 3H2O
[Cr(H20)3(OH)3] + 3OH- ------------> [Cr(OH)6]3- + 3H20

I believe [Cr(H2O)6]3+ is ruby

[wibletg]

(Original post by leeandrewarmstrong)
I believe [Cr(H2O)6]3+ is ruby

Green/Ruby/Violet are all valid I believe

[alan-93]

(Original post by leeandrewarmstrong)
I believe [Cr(H2O)6]3+ is ruby

it's ruby
and i thinnk the bond angle is 90, coz six ligands are bonded!

[Bright.Inspiration.]

Thank you

[Josh1993]

done! ruby is acceped. Its is 180 degrees as they are on the other side of the molecule.

[shuaib786]

(Original post by alan-93)
it's ruby
and i thinnk the bond angle is 90, coz six ligands are bonded!

agreed.

[Josh1993]

if anyone is intersted the paper is posted here.

http://www.thestudentroom.co.uk/show...=#post38231372

[Abbieastoria]

(Original post by alan-93)
it's ruby
and i thinnk the bond angle is 90, coz six ligands are bonded!

The way the question was worded I was under the impression they wanted the bond angle between the two water ligands which is 180


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[Josh1993]

I personally think AQA should award 5 marks to everbody for that percentage question, It would have put many off.
Their statement
http://web.aqa.org.uk/media-centre/news-200612.php

[shuaib786]

(Original post by Abbieastoria)
The way the question was worded I was under the impression they wanted the bond angle between the two water ligands which is 180


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Same here, i was deciding to either put 180 or 90.

[Abbieastoria]

(Original post by Josh1993)
I personally think AQA should award 5 marks to everbody for that percentage question, It would have put many off.
Their statement
http://web.aqa.org.uk/media-centre/news-200612.php

Didn't want to quote your entire mark
Scheme so...

For the entropy question, like, the graph one. I put 100JK-1mol-1 cos I timesed the 0.1 by 1000 but gave the new units as 100 joules rather than 0.1 kilo joules think I'll get the marks?


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