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1 Dec 2006 11:34:50 IST

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1009

chemical bonding

None

1} if bond angle is given how can we determine the s-orbital character of the hybrid orbital

2}energy required to dissociate 4gm of gaseous hydrogen into free gaseous atoms is 208kcal at 25degree celsius.The bond energy of h-h bond will be.

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arun-rashi

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2 Dec 2006 12:36:24 IST

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Actully each type of hybridisation have fix bond angle so we easily determine s charecter for example sp hyb bond angle 180,sp2 120,sp3109

ritumodi

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3 Dec 2006 14:46:05 IST

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i think u have not understood my point in question,i didnot asked for bond angle,the question i about s character

polymath

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3 Dec 2006 18:03:38 IST

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For the first question , i think the formula is

cos

= - (fraction of s-character)

for sp hybrid orbital, fraction of s-character = 1

cos

= - 1 and hence bond angle is 180 degrees. similarly you can work out

the others

polymath

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3 Dec 2006 18:06:49 IST

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So fraction of s character is negative of cos of bond angle. and you multiply it

with 100 and u get the % s- character. I dont know the exact relevance of this

formula. but i sort of worked it out for you today. So im sorry if it is wrong but it

works out for sp3, sp2, sp . so i think i might be right.

polymath

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3 Dec 2006 18:24:54 IST

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For the second question think that 2 moles of hydrogen need that much of

energy. so divide that amount of energy by 2 to get bond energy per mole i.e

bond energy of H-H bond at that specific temparature. i think it is 104kcal at 25

degrees celsius.

rosey

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7 Dec 2006 15:35:00 IST

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IN MOLECULAR ORBITAL THEORY,WHEN TWO ATOMIC ORBITALS MIX, IT HAS BEEN EXPLAINED BY CONSTRUCTIVE & DISTRUCTIVE INTERFERENCE . ELECTRON WAVES OF BOTH THE COMBINING ATOMIC ORBITALS WILL BE EITHER IN PHASE OR OUT OF PHASE,BUT WHY BOTH BONDING ORBITAL(due to in phase)AND ANTI BONDING ORBITAL(DUE IN OUT OF PHASE) ARE FORMED SIMULTANEOUSLY.

Qazi Mamoon

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4 Feb 2008 23:29:23 IST

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hey nooooo nooo nooo

Qazi Mamoon

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4 Feb 2008 23:31:09 IST

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sp orbital has 50% s character and 50% p
sp2 has 33% s character and 66% p

and so on..

for 4 gm H2 we have 208000 cal..
for 2 gm H2 we have 104000 cal..

maybe we need to take into consideration the temperature factor as well..

energy is 3/2 RT
3/2 (2) (273 + 25) as R is 2 cal/watever per watever
approx. 900 cal..

so the answer is shayad 104000+900 cal
=104900

correct me if i am wrong and salute if right..

Muneeb Shah

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4 Feb 2008 23:53:56 IST

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ooo jin.....
i think it is only 104000 cal...

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