Chemistry: Post your doubts here!

[sj0007]

that's easy... m worried abt p5 :/

Hey Can you help me with the molecular spectrum questions in A2 Chemistry..please

 

[mehria]

Hey Can you help me with the molecular spectrum questions in A2 Chemistry..please

yea sure...

 

[Bilal Khan]

Can some one help me with this PLZZZZZZZZZZZZZZZZZZZZZ!!!!!!!!
It is from May June 2010 Paper 42 Question 3(d)

The highest mass number is its molecular mass , that is 396 .
So try different possibilites to make 396 like 4 Si , 4 O and 9 Cl .

 

[princess Anu]

where can I find may june 07 chem?? please help
a link to the website maybe

 

[sj0007]

yea sure...

Thank you!!
Can you like brief a method we should approach or the FAQS??

 

[sj0007]

The highest mass number is its molecular mass , that is 396 .
So try different possibilites to make 396 like 4 Si , 4 O and 9 Cl .

So there is n other way just trial and error. Wouldn't it take alot of time??
I also did it the same way. But thought maybe I am wrong...look slike i was correct.

 

[sj0007]

yea sure...

Moreover what are the important things I need to know about NMR??

 

[The Chill Master]

where can I find may june 07 chem?? please help
a link to the website maybe

http://freeexampapers.com/?dir=A-Level/Chemistry/CIE/2007-Jun

 

[mehria]

Moreover what are the important things I need to know about NMR??

most important thing is to knw how to deduce the structure of a compound from the NMR spectrum by using chemical shifts and protons on data booklet...

 

[darks]

bio B, chem B n physics A

I know it's a bit awkward to ask but how did your chem paper went in AS that you got a B mine recently p22 went according to my expectations of around 40-43 marks
and i'm getting too worried

 

[sj0007]

most important thing is to knw how to deduce the structure of a compound from the NMR spectrum by using chemical shifts and protons on data booklet...

Hmm check I know that part...thank you so much
If I have any more doubts I might trouble you

 

[The Sarcastic Retard]

As in first 10 d block elements 4s is lower in energy and 3d is higher. so electron fills in 4s first and last in 3d.... then why does when any of the 10 element forms an ion the first electron is removed from 4s orbital?

 

[nehaoscar]

Like this one.http://maxpapers.com/wp-content/uploads/2012/11/9701_s14_qp_33.pdf

It's in the second experiment, c (i)

Sorry i know the practical is done and i'm replying late!
but yeah as i said earlier
thermometer error = 0.05
So % error
= (0.05/your reading) x 100

 

[mehria]

I know it's a bit awkward to ask but how did your chem paper went in AS that you got a B mine recently p22 went according to my expectations of around 40-43 marks
and i'm getting too worried

i screwed up in practical that's y i got overall B in chem... :/
u shud study hard to get better grades in p12 n p32/33
n everythng depends on gt...

 

[yoyoyoyoyoyoyoyoyoyo]

As in first 10 d block elements 4s is lower in energy and 3d is higher. so electron fills in 4s first and last in 3d.... then why does when any of the 10 element forms an ion the first electron is removed from 4s orbital?

As electrons fill the subshells 'd' and 's' ,they return back to their positions

 

[mehria]

Hmm check I know that part...thank you so much
If I have any more doubts I might trouble you

no prblm..

 

[mehria]

As in first 10 d block elements 4s is lower in energy and 3d is higher. so electron fills in 4s first and last in 3d.... then why does when any of the 10 element forms an ion the first electron is removed from 4s orbital?

4s is the outer most orbital so e- will be removed frm ths orbital first...
n do u knw the exceptions of electronic configuration in Cu n Cr?

 

[qwertypoiu]

As in first 10 d block elements 4s is lower in energy and 3d is higher. so electron fills in 4s first and last in 3d.... then why does when any of the 10 element forms an ion the first electron is removed from 4s orbital?

This link discusses this:
http://www.chemguide.co.uk/atoms/properties/3d4sproblem.html
Note that we don't actually have to know any of this, we just have to take it as a fact that 3d orbitals are filled first but 4s orbitals removed first...

 

[The Sarcastic Retard]

As electrons fill the subshells 'd' and 's' ,they return back to their positions

4s is the outer most orbital so e- will be removed frm ths orbital first...
n do u knw the exceptions of electronic configuration in Cu n Cr?

Well 3d is higher in energy than 4s so we fill 4s first that 3d. So 3d should be the one from which electron should be remove na.... Anyways this is wrong.. I got ma solution.

 

[The Sarcastic Retard]

This link discusses this:
http://www.chemguide.co.uk/atoms/properties/3d4sproblem.html
Note that we don't actually have to know any of this, we just have to take it as a fact that 3d orbitals are filled first but 4s orbitals removed first...

Ya, I got ma solution from this site. This site is really awesome... <3 My A level concepts are cleared from this site only.... Thanks to Jim. ^_^
Well.... to get in deep and understand, this will fit in memory and last forever... Rather than mugging up the facts.

The reason is simple... In K and Ca, 4s in lower in energy and in d block elements its different 3d is lower, not 4s! Coz of less repulsion more stability and who doesnt want stability in this world?