chemistry..

[maximum_user]

hi can anybody explain chemistry qp1 nov08...mcq no 39
nov09 qp1 mcq 5, 19, 21 &31

Plz do explain how yuo came up to the anszz..

 

[ds29]

Re: chemistry...a2(CIE alevels...)

W09 P11 Q5

Consider A Cl2 == Cl2 Chlorine is electronegative and therefore has a dipole. However the compound is symmetrical and therefore the dipoles cancel out.
Option C Both Chlorine and Oxygen are highly Electronegative. However again it is opposite directions and they cancel out.
Option D The Oxygen are placed symmetrically and therefore cancel out.

The correct answer is B, since even though H is placed in a symmetrical position it is not electronegative.

Q19
Ammonium Cyanate, let's resemble it using NH4(X) where X stands for the Cyanate ion.
Since no other products were formed CO(NH2)2 and NH4(X) should have equal number of Carbon, Oyxgen, Nitrogen and Hydrogen atoms.
Therefore we have 1 Carbon, 1 oxygen, 2 Nitrogens and 4 Hydrogen atoms.
Removing the already existing Nitrogen and 4 hydrogen atoms (which are in NH4) we are left with 1 Carbon 1 Oxygen and 1 Nitrogen.
That is A or B.
The answer is A since it's NH4+ therefore it's stoichiometrically equal, if we put 2+ then we'll have (NH4)2 which won't balance.

I'll work the others later, I've gotta go for a class!

 

[maximum_user]

Re: chemistry...

thanku...but i think u did it from the wrong question paper?