Edexcel CHEMISTRY DOUBTS!!!!

[@d!_†oX!©]

Can someone please explain resonance to me??
By the way that would be from CIE, but i don't think that should make much difference...soo...anyone? 

[nid404]

Resonance? :S Oscillations? That's physics 

[nid404]

but I'll explain it 

When the frequency of the external periodic of force and the body's natural frequency are equivalent, the body vibrates at it's maximum amplitude and this is known as Resonance.

[@d!_†oX!©]

Oh no no no!! 
I don't mean THAT resonance...i am asking about the resonance in chemistry
Let me give you the definition so you know what i am talking about

Resonance is due to delocalization of 'pi' electrons in a conjugated system

[nid404]

Ohhh ....I feel so embarrassed now  It didn't strike me 

This is a little difficult to explain so I got this from the net...hope you get it


It is a type of electron delocalization. Since electrons repel, if the electrons spread out, it can lead to greater stability.

In order for resonance to occur, you need to have a double bond (mobile high electron density) and a nearby orbital where the double bond can spread out to.

For example, in the following ion

H3C-CH=CH-CH2+

the double bond will be attracted to the positive charge and ends up spread out across two adjacent bonds.

H3C-CH=CH-CH2+ <---> H3C-CH-CH=CH2 (+ charge on carbon2)

Since the electrons are spreading out between the two states ("resonance structures") above, neither of those structures are really a good way to represent the molecule. The closest model of the molecule is a hybrid of the two, with the electrons smeared out over both spots where the double bond can exist. So, they are really each like a bond-and-a-half.

I got this from yahoo answers. I hope you understood.


If you don't understand, I can use benzene as an example which will be more convenient for me to explain.

[@d!_†oX!©]

I am sorry if I am being a too dumb but THIS concept goes above my head...even my teacher tried alot to explain resonance to me..hmm..

my question is, the example you used...isnt that "position isomerism", cuz all you are doing is transferring the double bond from on position to another...is it the mere fact that it is +vely charged that we call it resonance??

Oh my god...now i feel embarrassed..i know its not such a hard concept but i just cant get it...sorry for troubling you so much..

[nid404]

Oh no no....it's not isomerism.

I'll use benzene as an example. It has alternating single and double bonds. The structure oscillates between the two forms since the bonding electrons are delocalised.



This is a resonance hybrid when the structure keeps switching.

[The Golden Girl =D]

Hey everyone i got a doubt but i can really post it cuz it's in the book -__-

Anyways if u open the Exam Zone Unit 1 Test 1 Question 4)b) as well as C) and d) Please

and with Detailed Explanation Plz

Oh and i almost searched almost everywhere to find Amazing notes that give me ALL i need for Unit 1 chem lesson 2 , the section that talks abt enthalpy changes and the whole calculation thing in particular cuz i can't seem to make it FULLLY GLUE into my mind

Thanks *i'm off cuz i have Eng Essay to do -___- so will see this later iA *

FYI Edexcel Chem AS Book

[elemis]

Try and post a screenshot, more people can help you then.

[The Golden Girl =D]

Try and post a screenshot, more people can help you then.

I'm too embarrassed to say this but whatever ; i have No idea how to make a screen shot  

Well the Only i can do is that the thing is kinda similar to this actually it's the same i guess :

http://answers.yahoo.com/question/index?qid=20071123231452AAg8Kis

and the c part says 0.0500 mol of acid was neautralized in this reaction , calculate delta HEAT of neutralization in kJ/mol.

and part d says suggest y sodium hydroxide is used in SLIGHT excess ?    

thx

[elemis]

Near the top right hand corner of your keyboard there should be a button that says scrn shot.

Press it.

Open MS Paint.

Press   ctrl + V

Save the file in JPEG format.

Attach the picture here.

[The Golden Girl =D]

Near the top right hand corner of your keyboard there should be a button that says scrn shot.

Press it.

Open MS Paint.

Press   ctrl + V

Save the file in JPEG format.

Attach the picture here.

Thanks but the thing is I do NOT have a scanner after All O.O

So i really need help if not with the Question then in Fully GLUING the lesson in my mind (Enthalpy Changes and the calculation part of it *in AS  Chem*)

Plz , anyone ?

[nid404]

Is this the question? http://answers.yahoo.com/question/index?qid=20071123231452AAg8Kis

[The Golden Girl =D]

Is this the question? http://answers.yahoo.com/question/index?qid=20071123231452AAg8Kis

ya but some values i guess r diff :

50.0 cm-3of 1.00 mol dm-3 of HCl  with 50 cm-3 of 1 mol dm-3 NaOH  and temperature is 6.90

oh ya and b says Assuming the density is 1.00 g cm-3  and it's heat capacity is 4.18 K-1 g-1 , calculate the heat evolved during the reaction

it's exothermic By the way .

Thx Nid <3

[elemis]

If you have the chemistry AS Level LIVE-TEXT. You could take a screenshot and post here.