Chemistry: Post your doubts here!

[applepie1996]

Can u explain..i thought that excees of zinc will react so found tht one

excess if zinc is added to make sure that all the traces of zinc iodide is removed from the test tube
so basically you're just finding the amount of zinc that reacted with the iodine

 

[imperial]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w08_qp_2.pdf

3c (ii)

What is meant by half-equations?

 

[Dukeofwin]

Can someone tell me What is the drama of 4s shell being filled before 3d? And to what elements? I've read about it but it's so confusing.

 

[Gémeaux]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_2.pdf

3c (ii)

What is meant by half-equations?

Full equation is for the cell (after the cancelling of electron etc). Half equations are separate equations for each the anode and the cathode.
In this question that you have mentioned, only the equation from cathode is enough i.e.
2H+ + 2e–→ H2, and this leaves OH- ions in the remaining solution.

 

[iKhaled]

Can someone tell me What is the drama of 4s shell being filled before 3d? And to what elements? I've read about it but it's so confusing.

the 4s has a lower energy level than the 3d therefore it is filled first and all elements get their 4sfilled first except for chromium and copper.

 

[Dukeofwin]

the 4s has a lower energy level than the 3d therefore it is filled first and all elements get their 4sfilled first except for chromium and copper.

One line summary- Just what I wanted. Thanks more a Ton

 

[iKhaled]

One line summary- Just what I wanted. Thanks more a Ton

no problem

 

[Soldier313]

Basically, they'll allow it anywhere because I don't think it's incur syllabus to know why it'd be on the 4th carbon.
I, however came Accross it in my Internet search studies lol:
-with phenol, PARA (on the 4th carbon) substitution always occurs.
-IF para is blocked by another compound, the ORTHO occurs, which is C#2

oh okay thanx a lot!

 

[knowitall10]

Insha Allah andnthat too with great marks Ameen ! So which group do i need to stress upon ? And could you help me with paper 5 chemistry and physics best tips ? Like best ones?

I can help you with Chemistry, but i don't take Physics. If you want, i can help you with biology too.

 

[knowitall10]

Use c1v1= c2v2 for each column
so first Row workout With 0.1 NaOH is (0.1x24.3)/10
Note: we didn't conver cm3 to dm3 as both volumes are in cm3 else we would have to divide each volume by 1000

Btw, i just contacted my teacher regarding the use of C1V1=C2V2 in this question. He said that you cant use it here; even if it has to give the right answer. that formula is only used for dilution. yes you can use C1V1/n1=C2V2/n2 where n= no of moles.
I just thought it was important for all of us to know this...

 

[PANDA-]

C1V1 = C2V2 is only used when the number of moles before and after (1 -> 2) is equal, but concentration and volume change.

 

[knowitall10]

Can somebody please explain what's the "inert pair effect"? I dunno if it's in our course, but what i do know is that it was in the course last year or the year before that, so my teacher asked us to read it from the older version of our Chem book.
Jazakum Allahu Khair

 

[knowitall10]

C1V1 = C2V2 is only used when the number of moles before and after (1 -> 2) is equal, but concentration and volume change.

Yea, that's what my teacher just told me

 

[knowitall10]

Assalamu alykum fellow people Brothers and Sisters!
Can you please tell me what's the inert pair effect?
Jazakum Allahu Khair...

 

[Alice123]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_21.pdf
5dii my ans comes negative

 

[xhizors]

Btw, i just contacted my teacher regarding the use of C1V1=C2V2 in this question. He said that you cant use it here; even if it has to give the right answer. that formula is only used for dilution. yes you can use C1V1/n1=C2V2/n2 where n= no of moles.
I just thought it was important for all of us to know this...

well i don't knw it is only used for dilution i used the concept of titration here and a little of partition cofficient btw thanks

 

[MaxStudentALevel]

Btw, i just contacted my teacher regarding the use of C1V1=C2V2 in this question. He said that you cant use it here; even if it has to give the right answer. that formula is only used for dilution. yes you can use C1V1/n1=C2V2/n2 where n= no of moles.
I just thought it was important for all of us to know this...

Aw that's strange. Well it worked there.

 

[MaxStudentALevel]

Yea, that's what my teacher just told me

Hey, have you done MJ2008P5? My teacher keeps stressing I attempt it. Must be important. It's super confusing. Can you help me with the F part of Q2?

 

[iKhaled]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_21.pdf
5dii my ans comes negative

it is supposed to be +226

 

[MaxStudentALevel]

Hey,

it is supposed to be +226

Could you please help me with the (f) part of Q2 of MJ2008?