Chemistry: Post your doubts here!

[sumaiyarox:)]

4.6, i think.

how??

 

[sumaiyarox:)]

NMR is used to obtain the information about the number of hydrogen atoms and their chemical environment (to predict the structure of organic molecules ).
MASS SPECTROMETER is used to predict the relative atomic mass of the element,the different isotopes of the element and the relative abundance of the isotopes..
All chromatography techniques are used separate the different components in a copmound by using a mobile phase and a stationary phase..
but in each technique better mobile and stationary phases are used to make the results more reproducible and the separation more efficient.
TLC is similar to paper chromatography (PC) it has the same mobile phase (a polar solvent) as PC but a different stationary phase (slurry of silica or Al2O3),but the separation in TLC is better than that of PC because of the small size of the particles of stationary phase.
GLC uses an inert gas (N2 or Ne) as the mobile phase whereas stationary phase is inert porous diatomaceous rock which is packed in a glass column of narrow diameter (2mm), again the separation in GLC is better than TLC as the narrow diameter ensures the components to b in close contact with both stationary and moblie phase that increases the efficiency of separation... GLC is used to detect drugs in blood.
HPLC uses a high purity solvent as mobile phase that is puped under high pressures in the HPLC instrument , the stationary phase are the porous silica beads packed in a glass column of a narrow diameter, the results of HPLC is better than GLC... HPLC is used in the detection of explosive residues on the skin, it is used in the detection of pesticides in vegetables and fruits!

all dis asked in d papers?

 

[gary221]

all dis asked in d papers?

for knowledge, i guess.
i dont think this is asked.

pH = pKa + log([salt]/[acid])
pH = 4.76 + log(0.05/0.075)
solve to get pH = 4.6.

formula = pg 313 of coursebk

 

[sumaiyarox:)]

for knowledge, i guess.
i dont think this is asked.

pH = pKa + log([salt]/[acid])
pH = 4.76 + log(0.05/0.075)
solve to get pH = 4.6.

formula = pg 313 of coursebk

thnkkk uuu

 

[1357913579]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_41.pdf
4(C)
please someone help

 

[gary221]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_41.pdf
4(C)
please someone help

r u sure that's the right ppr?

 

[biba]

OOHHHHHHHHKK!!!!! I did not see that!!!!!! they were asking in the question abt acidified also....

THANK YOU SO MUCH

welcum

 

[biba]

all dis asked in d papers?

knowledge
but the uses or mobile and stationary phases of different chromatography techniques could be asked!

 

[sumaiyarox:)]

knowledge
but the uses or mobile and stationary phases of different chromatography techniques could be asked!

thnk uuu

 

[biba]

thnk uuu

u r welcum

 

[sumaiyarox:)]

u r welcum

 

[1357913579]

r u sure that's the right ppr?

really soory i meant 4(b)

 

[1357913579]

r u sure that's the right ppr?

in this question what iam confused is about why is b pb(so4) why not pb(so4)2 how in the exam would i know this?

 

[gary221]

in this question what iam confused is about why is b pb(so4) why not pb(so4)2 how in the exam would i know this?

pg 355 coursebk
the +2 oxidation state in lead compounds is much more stable than the +4 state.
So, it reduces to the +2 state ---> and forms PbSO4

 

[1357913579]

pg 355 coursebk
the +2 oxidation state in lead compounds is much more stable than the +4 state.
So, it reduces to the +2 state ---> and forms PbSO4

thanks a lot bro
bro can u please list anything now in the cie book but in the syllabus please?

 

[1357913579]

thanks a lot bro
bro can u please list anything now in the cie book but in the syllabus please?

i meant things which are not in the cie book but are in the syllabus

 

[gary221]

i meant things which are not in the cie book but are in the syllabus

i think everyth's almost thr in the bk, i dont know wht exactly is thr in the syllabus, nvr checked...

 

[1357913579]

i think everyth's almost thr in the bk, i dont know wht exactly is thr in the syllabus, nvr checked...

for A2 inorganic do we have to also memorize AS reactions? becuase in the oct/nov papers they hve asked many question from AS have u seen it?

 

[gary221]

for A2 inorganic do we have to also memorize AS reactions? becuase in the oct/nov papers they hve asked many question from AS have u seen it?

yes, v need to

 

[1357913579]

yes, v need to

no time