Chemistry: Post your doubts here!

[knowitall10]

[^__^].. yeah i know, our chem sir did correct some mistakes in it... wel i have learned the concepts, so now i think it would be wise to do the pastpapers?.. cuz i did my core with the pastpapers em just left with the applications :/

Chem Guide...use this website. the application booklet has messed up concepts...

 

[Student12]

Can anyone explain the effect of concentration when doing the prefrentional discharge? HELPPP!

Anyoneeee!?

 

[iKhaled]

Anyoneeee!?

what does that mean ? " prefrentional discharge"

 

[knowitall10]

what does that mean ? " prefrentional discharge"

The thing i explained remember?

Student12 look at @xhizor's thread on chem and phy doubts. i explained it there in the first few pages. if u dnt find it,tell me

 

[knowitall10]

https://www.xtremepapers.com/commun...eypoints-notepoints-ondemandonly.25941/page-8

 

[iKhaled]

The thing i explained remember?

Student12 look at @xhizor's thread on chem and phy doubts. i explained it there in the first few pages. if u dnt find it,tell me

the discharge of anions at the elctrodes?

 

[kkhizar1]

Nov 11 Paper 43 Q3(e) iv.... why is the concentration of CH3COOH 0.075 and not 0.025 and how do we get 0.05 for CH3COONa... The marks scheme is not clear and I cant find the examiner report. Please help

 

[Student12]

Pleas

The thing i explained remember?

Student12 look at @xhizor's thread on chem and phy doubts. i explained it there in the first few pages. if u dnt find it,tell me

please just brief it.. Or direct me to the page help Karo na pls! ;D

 

[Student12]

the discharge of anions at the elctrodes?

Effect of conc of the ions

 

[Xtremite]

Effect of conc of the ions

Effect of concentration is only for Chloride ions, Bromide ions, iodide ions and Hydroxide ions. In a concentrated solution of these ions, no matter what the reactivity of the other anion is, the anion (the ones i mentioned) will be preferentially discharged.

I hope this clarifies your confusion.

 

[knowitall10]

Pleas please just brief it.. Or direct me to the page help Karo na pls! ;D

I just did

 

[knowitall10]

Assalamu 'Alaykum.
Can somebody please post the link to the winter 2011 examners' report?
Jazakum Allahu Khair.

 

[knowitall10]

Assalamu 'Alaykum.
Can somebody please post the link to the winter 2011 examners' report?
Jazakum Allahu Khair.

alright never mind, thanks.

 

[strangerss]

Does structural formula mean we have to draw the skeletal formula....for eg can't we write CNCH2CH2CH2CN instead of drawing it in a skeletal form...please please reply
In ms they usually give the skeletal..but isnt the formula i wrote about also structural?

what you wrote is the structural formula and the skeletal formula is completely different

 

[strangerss]

Can someone please help with p34 Oct/Nov 2012 question( g) I didn't know how to find the mean :S

 

[raamish]

in qs 7c(ii) n09 41 how did we determine that 0-ch3 is on 4th position on benzene ring?
answer plzz

 

[messi10]

Can anyone list most poplar electron withdrawing and donating groups?

Regards

 

[biba]

Can anyone list most poplar electron withdrawing and donating groups?

Regards

electron donating groups ; all alkyl groups, -OH, -NH3 ,-OCH3, -N(CH3)2...........
withdrawing groups : -NO2 , -SO3H , -COOH , -CN , -CHO , -CO- , -CO2- , -CONH2- , -CONH-

 

[biba]

in qs 7c(ii) n09 41 how did we determine that 0-ch3 is on 4th position on benzene ring?
answer plzz

em not very good at expalining things..
first go through the notes that i have attached and then try to understand this :
first find the number of carbon atoms by [(100/1.1)x(M+1/M)]
3H gives a singlet,which means that they are directly attached to the more electronegative element or the functional group.. these 3H give u a singlet at chemical shift value of 3.6.. the group is -OCH3...
1H also gives you a singlet at 5.6 that is the chemical shift value of phenol
than the 4H also gives you a singlet so these are the hydrogens of the benzene ring so ur formula becomes
1,4 methoxyphenol.. (the -OH group is on the 1 position of benzene and as it is an electron donating group the -OCH3 is on the 4th position)
i knw my explanation is pathetic ...still...

 

[messi10]

electron donating groups ; all alkyl groups, -OH, -NH3 ,-OCH3, -N(CH3)2...........
withdrawing groups : -NO2 , -SO3H , -COOH , -CN , -CHO , -CO- , -CO2- , -CONH2- , -CONH-

Thank you so much for the help.

Also,
Can you please tell the effect of electron withdrawing and donating groups attached to benzene ring?

I mean, for example if Cl is going to add in benzene in presence of AlCl3
I get confuse on which position to add the Cl (ortho, meta or para), if electron donating is attached and on which to add if electron withdrawing is attached.

I need a little briefing on it.

Your help is appreciated.
Best Regards