Author Topic: more cie chem doubts  (Read 1043 times)

Offline Sue T

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more cie chem doubts
« on: December 26, 2009, 10:21:49 am »
(ppr 2)in nov 04 ques 3 (a)iii
at the anode th oxidation number goes from -1 to 0 (oxidation)
at the cathode the oxidation num is supposed 2 go from +1 to 0 (reduction)
th ms says -1 to 0 at th cathode- is t a mistake?

one more question  ;D
nov05 Q2 (d)
shouldnt it be like : -395+(2*-298)+(delta H formation) = -1110      ???
its exothermic since bonds r formed so the answer must be negative
but in th ms its positive (they did it in a diff way)
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Offline Lana Wolf

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Re: more cie chem doubts
« Reply #1 on: December 26, 2009, 10:34:48 am »
the papers arent opening... :S
some prob in freeexampapers..??

nid404

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Re: more cie chem doubts
« Reply #2 on: December 26, 2009, 01:38:08 pm »
nov 04....that's a mistake..

nov 05
 
You need to calculate enthalpy change of formation of CS2

so C+2S`--->CS2

S+O2--->SO2 -298kj/mol   X2
C+O2--->CO2   -395kj/mol
CS2+3O2---> CO2+2SO2 -1110kj/mol

-395+ (-298X2)+dh--->1110 (become postive because it is on the other(product)side of the main reaction)
dh=1110-(991)
=+119kj/mol




Offline Sue T

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Re: more cie chem doubts
« Reply #3 on: December 26, 2009, 05:14:05 pm »
OOooo! got it
thx alot again!  ;)
Knowledge is knowing a tomato is a fruit; Wisdom is not putting it in fruit salad.

Offline sweetie

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Re: more cie chem doubts
« Reply #4 on: January 01, 2010, 02:31:10 pm »
Hey,
am also confused about Q4 parts "c" and"d" of paper2 nov04

Offline sweetie

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Re: more cie chem doubts
« Reply #5 on: January 06, 2010, 03:30:55 pm »
can any1 plz help me in Q.10 of nov07 paper1????????????
how can the conc of 2NO2 be 2.4??????????????? :'( :'( :'(

nid404

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Re: more cie chem doubts
« Reply #6 on: January 06, 2010, 05:09:44 pm »
conc of NO2 will be conc of O2 +N2(0.8+1.6)
Ratio of O2 to N2 is 1:2...so [N2] is 0.8X2=1.6

Offline sweetie

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Re: more cie chem doubts
« Reply #7 on: March 31, 2010, 03:32:21 pm »
Thank You :-*