Chemistry: Post your doubts here!

[nehaoscar]

Its not like that. The peak of c is at 450 nm which means that it absorbs all of blue and gives out its complementary color, red and the same thing happens at peak of D, it absorbs all of rwd and gives out the complementary color which is blue.

Ohhh so do you look at the point where it touches the x axis (zero absorbance) for it's colour?

 

[talal096]

Someone told me chemistry AS syllabus changed. Will it effect these Oct/nov 2015 papers as well?
What are the new topics and which topics are removed? Plzz HELP!!!

 

[nehaoscar]

Someone told me chemistry AS syllabus changed. Will it effect these Oct/nov 2015 papers as well?
What are the new topics and which topics are removed? Plzz HELP!!!

No the changes take place from 2016 papers

 

[psychiatrist]

http://onlineexamhelp.com/wp-content/uploads/2014/08/9701_s14_qp_22.pdf
Q2 part iii, iv and v
ASAP

 

[The Sarcastic Retard]

http://onlineexamhelp.com/wp-content/uploads/2014/08/9701_s14_qp_22.pdf
Q2 part iii, iv and v
ASAP

(iii) We are asked to find number of moles of compound in 250cm^3 we found its mole in 25cm^3 in part (ii)
--> (250 * 5 * 10^-3)/25 = 0.05 mol
(iv) Mr = m/n = 6.3/0.05 = 126
(v) Mr of H2C2O4 = 90
So 126 - 90 = xH20
That is 36
Mr of H2O = 18 so x is 2

 

[darks]

Guys i am giving AS this O/N and what i see from past papers is that in recent years the examiner is giving stuff that rarely comes in our exams (e.g position/chain isomers... catalytic convertors and few organic reactions..)
please please please i will be really thankful if anyone could make a small (or maybe big or maybe a single thing) list of things that people usually forget/ miss after doing past papers as it rarely came any year. I am sure that can help everyone giving AS this o/n
thanks in advance

 

[The Sarcastic Retard]

Guys i am giving AS this O/N and what i see from past papers is that in recent years the examiner is giving stuff that rarely comes in our exams (e.g position/chain isomers... catalytic convertors and few organic reactions..)
please please please i will be really thankful if anyone could make a small (or maybe big or maybe a single thing) list of things that people usually forget/ miss after doing past papers as it rarely came any year. I am sure that can help everyone giving AS this o/n
thanks in advance

All you need is a good grasp on the concept. That's it.
Still 2 days are there, practice as many things u can.... But remember u should know ur every concepts.

 

[Metanoia]

Guys i am giving AS this O/N and what i see from past papers is that in recent years the examiner is giving stuff that rarely comes in our exams (e.g position/chain isomers... catalytic convertors and few organic reactions..)
please please please i will be really thankful if anyone could make a small (or maybe big or maybe a single thing) list of things that people usually forget/ miss after doing past papers as it rarely came any year. I am sure that can help everyone giving AS this o/n
thanks in advance

With so little time left, it makes more sense to focus on the main and common concepts rather than a list of "unexpected questions".

Such a "list" will never be accurate nor exhaustive; and would only add unnecessary stress instead.

 

[awesomaholic101]

http://gopapers.net/alevel.html?_9701_w13_ms_22
Question 2.b.ii) Can anyone please explain how the first and second structures is not the same??

 

[The Sarcastic Retard]

http://gopapers.net/alevel.html?_9701_w13_ms_22
Question 2.b.ii) Can anyone please explain how the first and second structures is not the same??

Optical isomer.

 

[sj0007]

can anyone tell me the two geometric isomers of 3-methyl-2-pentenoic acid (CH3CH2C(CH3)=CHCO2H)?
I am confused...............

 

[Metanoia]

can anyone tell me the two geometric isomers of 3-methyl-2-pentenoic acid (CH3CH2C(CH3)=CHCO2H)?
I am confused...............

There is EZ isomerism at the C=C double bonds.

 

[awesomaholic101]

Optical isomer.

How? There's no chiral carbon

 

[The Sarcastic Retard]

awesomaholic101

 

[awesomaholic101]

awesomaholic101

Ok i think i got it ... Thank u

 

[sj0007]

There is EZ isomerism at the C=C double bonds.

Thnx............also is the cis - trans isomerism the same as EZ isomerism?

 

[sj0007]

Can anyone please name the structure: CH3CH(OH)C(CH3)=CH2?
Thnx...........

 

[awesomaholic101]

Can anyone please name the structure: CH3CH(OH)C(CH3)=CH2?
Thnx...........

3-methylbut-3-en-2-ol

 

[sj0007]

3-methylbut-3-en-2-ol

Thnx.............
So we always start the numbering from the other functional group rather than the double bond? Ryt?

 

[awesomaholic101]

Thnx.............
So we always start the numbering from the other functional group rather than the double bond? Ryt?

Yea,the substituent gets named first, next the double bond, then hydroxyl group ...
But we number the carbons so that hydroxyl group gets the lowest number possible