Chemistry: Post your doubts here!

[Ebrahim12]

how can we determine element b and c are in group 2 and 1,but not group 12 and 11? should we refer to data booklet for checking the standard 1st ionisation energies to get the elements and correct group?

You're looking for a jump in successive ionization energies, which means that all the outermost electrons were removed and the next one is in an inner shell.

B has a jump between two and three, which means that it has two valence electrons, group 2.
C has a jump between one and two, one valence electron, group 1.

 

[jinggggg]

You're looking for a jump in successive ionization energies, which means that all the outermost electrons were removed and the next one is in an inner shell.

B has a jump between two and three, which means that it has two valence electrons, group 2.
C has a jump between one and two, one valence electron, group 1.

why can't theybe group 11 and 12?

 

[student3737]

Can someone help with this winter 2009 paper? Question 7, I got how to get carbon and hydrogen but how do you find the number Of oxygen and the overall structure of the compound ?

 

[Mushraf altaf]

I'm confused with this one. The CH group is connected to an benzene and an oxygen, so both fit the 2.7 ppm and 4.0 pp,m option in the question.
and OH can be any of the two (because its range is anywhere between 0.5-6.0 ppm). How can I know whether that the CH group shows ppm of 2.7 because its an Alkyl next to an aromatic group OR whether it shows ppm of 4.0 because its next to an electronegative atom (Oxygen).

also if there are some good notes or examples on analytical techniques ( NMR especially) pls provide a link to me, I'm confused with it.

thank you!!!

 

[Khitan]

Those studying A2 this year.
How are you guys Keep revising this Reaction of Organic?
If i dont revise for 4-5 days,I will forget the Catalyst or reagent.
Cant Find any summary on Internet like we have of AS reactions.
Like 1 or 2 page summary reactions

 

[Kanekii]

Those studying A2 this year.
How are you guys Keep revising this Reaction of Organic?
If i dont revise for 4-5 days,I will forget the Catalyst or reagent.
Cant Find any summary on Internet like we have of AS reactions.
Like 1 or 2 page summary reactions

Which reaction?
I hope this helps
I found this a while ago from somewhere in this forum, full credit goes to that guy.

 

[Khitan]

Which reaction?
I hope this helps
I found this a while ago from somewhere in this forum, full credit goes to that guy. View attachment 64569

Ohh grea888!

 

[helloolo]

Hey guys could you please explain why its not [Zr2(C2O4)4] the mark scheme is saying the answer should be [Zr(C2O4)4]^4-

 

[Hamnah Zahoor]

Hey guys could you please explain why its not [Zr2(C2O4)4] the mark scheme is saying the answer should be [Zr(C2O4)4]^4-

Because the complex you formed contains two Zn^4+ while it says in the question it should include only one.
Don't try to balance out the complex to make the net charge zero.

 

[helloolo]

Because the complex you formed contains two Zn^4+ while it says in the question it should include only one.
Don't try to balance out the complex to make the net charge zero.

Thank you i didn't read the question properly.

 

[Hamnah Zahoor]

Thank you i didn't read the question properly.

You are welcome

 

[Kanekii]

Why is this complex not octahedral though?
Shouldnt the Coordination No.=6?

 

[Hamnah Zahoor]

Why is this complex not octahedral though?
Shouldnt the Coordination No.=6?

No it's tetrahedral and the cordination number is 4 not 6.
Four ethanedioate ions are attached to Zn4+ .

 

[Showmmo]

Can somebody provide me with the link for February March 2019 CIE As level Chemistry, physics and maths question paper.
If somebody have it only downloaded please email me the file.
[email protected]

Thanks.

 

[Garry Soloan]

Can someone explain the answers of C(i) and C(ii) ?
I attached the question and mark scheme
paper code: 9701/42/F/M/18

 

[sukasukinya]

Hey guys, please help me? The question asks for the reaction of serotonin with Br2 but the mark scheme says that only phenol reacts with it. Doesn't alkene c=c react too? I need an explanation for this. I'm so scared for coming exam

 

[Kanekii]

Can someone explain the answers of C(i) and C(ii) ?
I attached the question and mark scheme
paper code: 9701/42/F/M/18View attachment 64606 View attachment 64607

 

[Hamnah Zahoor]

Hey guys, please help me? The question asks for the reaction of serotonin with Br2 but the mark scheme says that only phenol reacts with it. Doesn't alkene c=c react too? I need an explanation for this. I'm so scared for coming exam
View attachment 64611View attachment 64612View attachment 64613

Conditions for adding a bromine across the double bond are not being fulfilled .
Solvent CCl4 is not present bromine is in aqueous form.

 

[Ebrahim12]

may june 2016 42

Can someone explain why in the ms they take the concentration of ch3nh2 as y instead of y - 3.966 x10^-4 ?

 

[Kanekii]

Need help with (ii)