Chemistry: Post your doubts here!

[Xtremite]

ian not saying that br2 is wrong what iam asking is that is diazotizationn coupling correct or not?

Of course it's correct now that the mark scheme has mentioned it. But why bother? When you can perform a simple test which you have learnt in O level, why go into these complicated tests!

 

[1357913579]

Of course it's correct now that the mark scheme has mentioned it. But why bother? When you can perform a simple test which you have learnt in O level, why go into these complicated tests.

ok thanks alot for your cooperation

 

[Xtremite]

ok thanks alot for your cooperation

Never mention it, long-number.

 

[knowitall10]

Never mention it, long-number.

LOL!!
Sorry dude...got blind for fraction of a sec I ddnt c it
but thanks a lot! Jazaki Allahu Khair

 

[iKhaled]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_43.pdf
Q 3 e (iv)
Yalla....show us

Silent Hunter

alright here is the solution...

first of all we write the equation to check the molar ratio and its CH3COOH + NaOH ---> CH3COONA + H20

now lets calculate the number of moles of the acid and base before the reaction
n of ethanoic acid = 0.25x(10/1000) = 0.0025 mol
n of NaOH = 0.1x(10/1000) = 0.001 mol

now when we mixed them together the total volume of the solution will be 20cm^3 so u can see that ethanoic acid is in excess and the ratio of acid:base:salt is all 1:1:1 so 0.001 mol of salt will be produced and that has a concentration of 0.001/0.02 = 0.05mol/dm^3 and the acid left unreacted in the solution will be 0.0025-0.001 = 0.0015 mol so the concentration of the acid will be 0.0015/0.02 = 0.075

use the equation PH = 4.76 + log(0.05/0.075)
PH = 4.58

thats it..hope u got it!!

 

[biba]

doing the application chapters from the application booklet and chemistry coursebook (roger norris) is enough ryt ?

 

[iKhaled]

doing the application chapters from the application booklet and chemistry coursebook (roger norris) is enough ryt ?

i heard loads of negative feedback about the application booklet..so u better not waste ur time on it !

 

[biba]

i heard loads of negative feedback about the application booklet..so u better not waste ur time on it !

[^__^].. 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 :/

 

[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.