Chemistry P4| A2 only

[maybeitwasnoone]

Need help in Nov 2008 Q4 b (iii)
QP- http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_qp_4.pdf
MS- http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_ms_4.pdf
Please help.
Thank you in advance!

 

[saudha]

can some body wht is partition coeffficient an explain it ........or give me a link related to it

 

[smzimran]

can some body wht is partition coeffficient an explain it ........or give me a link related to it

http://www.chemguide.co.uk/CIE/section112/learningf.html

http://www.docbrown.info/page07/equilibria4.htm

 

[saudha]

http://www.chemguide.co.uk/CIE/section112/learningf.html

http://www.docbrown.info/page07/equilibria4.htm

thankyou

 

[hassam]

smzimran m asking abt assumption part in next part of question

 

[histephenson007]

Can anyone explain why lattice enthalpy is positive (endothermic) when we are talking about solubilities of Group II sulphates. But becomes negative (exothermic) when we are talking about the Born-Haber Cycle????????? dafuq?

 

[smzimran]

hassam:
Ok sorry i misread ur first post
We assume temperature is the same, Remember this is the initial temperature we are talking about
The heat evolved would be more as it is an exothermic reaction so the change in temperature would be different in the end

But initially we keep the temperature same!

 

[angelgirl:)]

Can anyone explain why lattice enthalpy is positive (endothermic) when we are talking about solubilities of Group II sulphates. But becomes negative (exothermic) when we are talking about the Born-Haber Cycle????????? dafuq?

grp II the polarising power dec..down the grp...so its difficult to break them...thats y more enery is needed as u go down the grp...
but for the Born-Haber..the reactants r already in gaeous atomic form so they have to just combine with eachother to form a solid ionic compound...so it realese energy..

 

[smzimran]

Can anyone explain why lattice enthalpy is positive (endothermic) when we are talking about solubilities of Group II sulphates. But becomes negative (exothermic) when we are talking about the Born-Haber Cycle????????? dafuq?

Its always negative, where did you see it positive ?
It may be less exothermic (less negative) or more exothermic (more negative) but it is never endothermic!
Check this

 

[hassam]

u mean temp of water in which i ll be dissolving the solid....hmm got it cos in hot solution solubility will be different compared to that in cold ....so we must be dissolving both solids in the solution at same temperatire ryt?
and why we acidify feso4 when titraating it with mno4....is it to provide H+ ions or to make it stable to oxidation so that it is not oxidised b4 titration is started by oxygen from air

 

[smzimran]

u mean temp of water in which i ll be dissolving the solid....hmm got it cos in hot solution solubility will be different compared to that in cold ....so we must be dissolving both solids in the solution at same temperatire ryt?

Exactly!

 

[smzimran]

and why we acidify feso4 when titraating it with mno4....is it to provide H+ ions or to make it stable to oxidation so that it is not oxidised b4 titration is started by oxygen from air

To provide H+ ions

 

[hassam]

well but will not a feso4 solution get oxidised if lleft in air like an apple goes brown.....chek it urself.....fe3+/fe2+ equilibrium has +.77 whereas an oxygen equilibrium will have a more positive e naught value

 

[angelgirl:)]

What are thermoplastic or thermosetting polymers?

 

[smzimran]

well but will not a feso4 solution get oxidised if lleft in air like an apple goes brown.....chek it urself.....fe3+/fe2+ equilibrium has +.77 whereas an oxygen equilibrium will have a more positive e naught value

Yes, but manganate also has to be oxidised, right ?
And it needs H+ ions

MnO4- + 5e- + 8H+

Mn2+ + 4H2O

 

[smzimran]

What are thermoplastic or thermosetting polymers?

The difference b/w the two:
Thermoplastics can be melted down and moulded into something different, hence why they are so easy to recycle. Where as thermosetting plastics cannot be melted down after it has already set.


This is due to the bonds in the hydrocarbon formula (plastics are made out of hydrocarbons, hydrogen and carbon atoms). Thermoplastics have an alkene bond which means the hydrocarbon shares an atom with two bonds making it more reactive; and hence easy to recycle. Thermosetting on the other hand has normal bonding.

 

[hassam]

anser?

 

[angelgirl:)]

how to get the initial rate from the gragh..i didnt get y they took (0.9-1.1)*10^-3....?
Q2biii
Q3ai...how the -CHO grop changed to -NH2 and -CN...Y NOT to -OH and -nitryl...?
e iv...how did they got 0.075...and y did they divide acid upon salt,isnt it the opposite?
Q5biv...how to calculate the ratio?

 

[Zishi]

anser?

2,6-dibromo-4-chlorophenylamine

 

[Ayaaa]

how to get the initial rate from the gragh..i didnt get y they took (0.9-1.1)*10^-3....?
Q2biii
Q3ai...how the -CHO grop changed to -NH2 and -CN...Y NOT to -OH and -nitryl...?
ii...wats the intermediate?

I will show you tomorrow!