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Edexcel CHEMISTRY DOUBTS!!!!

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Deadly_king:

--- Quote from: Ang3l on January 19, 2012, 08:21:38 pm ---Plus the above, can any also make trans-esterfication clear for me :S

Trans-esterification is fine for me now
but ofcourse I have another doubt :P

(attached) How is it D :S

Thanks


--- End quote ---

Firstly let's look for compounds which have optical isomers, i.e chiral centres!

This leaves us with only option B and D since A and C can in no way show chirality!

Now we look for E-Z isomers, only D is right for B has two methyl groups attached to the carbon containing the double bond! So it cannot show E-Z isomers.

Hope it helps :)

KJ1995:

--- Quote from: Ang3l on January 19, 2012, 02:03:44 pm ---Thanks GG :D

Can anyone do this question for me :S

I don't understand why the volume is 12.5 :s

Q20 a(v)

Another doubt:

Why does diluting a weak acid increase its degree of dissociation? :S

--- End quote ---
When we add water the system trys to oppose the change (chattliers principle) by using up the water added which shifts equilibrium to the right, which means more [H+] and [CH3COO-], and less [CH3COOH].. putting those new values in the (Ka) equation will make the value of Ka bigger...and i also dont know why is it 12.5, can you please tell em when you find out?
Thank you

~ Miss Relina ~:

--- Quote from: Ang3l on January 19, 2012, 08:21:38 pm ---Plus the above, can any also make trans-esterfication clear for me :S

Trans-esterification is fine for me now
but ofcourse I have another doubt :P

(attached) How is it D :S

Thanks


--- End quote ---


I'm sorry for interfering but are there any links which helped you out in Trans-esterification  point
Thanks in advance  ???

Malak:

--- Quote from: ~ Miss Relina ~ on January 20, 2012, 01:15:49 pm ---
I'm sorry for interfering but are there any links which helped you out in Trans-esterification  point
Thanks in advance  ???

--- End quote ---
I used the text-book and the edexcel revision guide.
I dont think we need to know very much about it and the revision guide gave me enough detail needed.

The Golden Girl =D:
Q.20 how come it's 12.5 ?!


Okay from the First part of the Question we know that in the Titration 0.25 moldm-3 of NaOH and 0.125 moldm-3 of Ethanoic Acid  !!


so What I did is I found the Ratio as follows =>       Acid : Base
                                                          
                                                                      0.125 : 0.25  divide by 0.125 for both

                                                      I  get a Ratio of => 1 : 2

And from the part (v) we get to know that  25 cm3 of the ACID is USED UP !!!  .. so to find the Volume at the End point (Where the salt/product is given indicating that the ACID is completely KILLED) is

                                                               1  : 2

                                                               25 :  X      

Cross multiply and You'll find that the Volume of the BASE is  =>                   12.5 cm3


I simply used my common sense and it worked :D


if it doesn't work Use the formula from the CIE board (not in the syllabus) ;

(C1V1) acid =  (C2V2)base.... and act smart ;D

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