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Author Topic: Edexcel CHEMISTRY DOUBTS!!!!  (Read 268594 times)

Offline Malak

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1215 on: May 27, 2011, 09:39:35 am »
Good luck everyone today :D

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Offline NidZ- Hero

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1216 on: May 27, 2011, 10:17:11 am »
Leaving  For the exam GOOOOOOODDDDD LUCK EVERYONE

Hope it all goes well


Inshaallah
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Offline NidZ- Hero

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1217 on: May 27, 2011, 10:17:41 am »
Quote from: ang3l on May 27, 2011, 09:39:35 am
Good luck everyone today :D



Angel Chill its goonna be cool :0
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Offline Malak

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1218 on: May 27, 2011, 10:23:51 am »
Quote from: Nidzzz on May 27, 2011, 10:17:41 am
Angel Chill its goonna be cool :0
Lol..Yeah

That was just a goodluck wish  ;)
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Offline angelofhope

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1219 on: May 28, 2011, 11:24:04 am »
Quote from: Nidzzz on May 26, 2011, 09:00:59 pm

No it doesnt

really? umm.. isnt water a nucleophile? it forms dative covalent bonds where the transition metal complexes are formed right? im  not sure  ???
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elemis

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1220 on: May 28, 2011, 11:31:15 am »
Quote from: angelofhope on May 28, 2011, 11:24:04 am
really? umm.. isnt water a nucleophile? it forms dative covalent bonds where the transition metal complexes are formed right? im  not sure  ???

Yes, you are correct. Nucleophiles do, at times, form dative covalent bonds with other reactants.
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Offline NidZ- Hero

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1221 on: May 28, 2011, 12:06:30 pm »
oPps sry
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Offline Ghayth

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1222 on: May 28, 2011, 12:55:16 pm »
The question goes like this,
State and explain wether the following reaction can occur.
3Fe2+ ----> Fe + 2Fe3+


Given :
Fe3+ + e- ---> Fe2+     +0.77v
Fe2+ + 2e-  ----> Fe      -0.44v

Can someone please help ? My teacher seemed to flip the signs on some of the E values and I can't seem to figure out why.
Thanks  :)
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Offline shwe

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1223 on: May 28, 2011, 04:21:48 pm »
that's a yes, the reaction would occur.
If you add two E values, it would give you the "positive" values. As you may know, the reaction is feasible if the E value is positive.
And you don't have to multiply each E values or change the sign since E is not affected with coefficient of equation.
I hope it helps.
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Offline Ghayth

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1224 on: May 28, 2011, 04:26:44 pm »
Thats weird my notebook says the solution is :
E of cell= -0.44-0.77= - 1.21V , rxn is not feasible.
I'm confused  :-\
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Offline shwe

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1225 on: May 28, 2011, 04:39:09 pm »
Oppss, what was I thinking,
ya, the sign should be reverse, making it negative, since the question is from Fe2+ to 3+ but the equation is from Fe3+ to 2+ .
tht's not feasible.
sorry mate, for not reading the question well enough.
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Offline Ghayth

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1226 on: May 28, 2011, 04:39:50 pm »
Ooh I just got it , damn its simple lol .. no problem man thanks
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Offline angelofhope

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1227 on: June 01, 2011, 06:34:23 am »
hey.. can anyone help me with this question?

what do u observe when a piece of copper metal is added to Cr3+(aq) solution? explain ur answer by using the electrode potentials given below.

Cr3+(aq) + 3e- -------> Cr(s) E cell value = -0.77 V

Cu2+ + 2e- -------> Cu(s) Ecell value = +0.34 V

Thanks =D
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Offline wakemeup

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1228 on: June 02, 2011, 11:17:25 am »
Quote from: angelofhope on June 01, 2011, 06:34:23 am
hey.. can anyone help me with this question?

what do u observe when a piece of copper metal is added to Cr3+(aq) solution? explain ur answer by using the electrode potentials given below.

Cr3+(aq) + 3e- -------> Cr(s) E cell value = -0.77 V

Cu2+ + 2e- -------> Cu(s) Ecell value = +0.34 V

Thanks =D



I'm not 100% sure but I think that nothing should happen. Chromium has the tendency to lose electrons according to the E cell value and the solution already has Cr3+ ions in it. Copper ions have the tendency to gain electrons as shown by the standard potential and there are no Cu2+ ions in the solid copper metal. Therefore there is no initiative for either element to lose or gain electrons and no reaction should take place.

Again, I'm not completely sure if what I'm saying is right so it would be great if someone could confirm or correct my answer.
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Offline angelofhope

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1229 on: June 02, 2011, 07:26:38 pm »
Thanks.. dats da correct answer.. i've don't some research too.. and dats da anwer i got  ;)
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