• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Chemistry: Post your doubts here!

Messages
1,394
Reaction score
1,377
Points
173
in my topical answers...
but i dont have the mark scheme of it. :(
see the deal is that if we are considering the PERCENTAGE of elements in the compound it is just like if we are taking 100g of the substance and then saying that e.g. 33.4g of it is C.
but the thing here is that if u add all the percentages we get 99.97% which means that a 0.03% part of the whole compound is unknown... it is prob something other than these three elements....
now if it is not an authentic source of cie papers (or even if it is) my guess wud be that they misprinted the question so dont fret over it all too much bcz ur method is definitely correct if u did it like u said u did...
other than that we can still be open for suggestions from other fellows and see if anyone has an explanation.
 
Messages
6,392
Reaction score
27,000
Points
698
namehere has some explanation...
let's see... ok..
thanks for your help. :)
see the deal is that if we are considering the PERCENTAGE of elements in the compound it is just like if we are taking 100g of the substance and then saying that e.g. 33.4g of it is C.
but the thing here is that if u add all the percentages we get 99.97% which means that a 0.03% part of the whole compound is unknown... it is prob something other than these three elements....
now if it is not an authentic source of cie papers (or even if it is) my guess wud be that they misprinted the question so dont fret over it all too much bcz ur method is definitely correct if u did it like u said u did...
other than that we can still be open for suggestions from other fellows and see if anyone has an explanation.
 
Messages
1,394
Reaction score
1,377
Points
173
upload_2014-4-13_12-2-31.png

how many moles of H2 will be produced when 1 mol of this acid reacts with an excess of Na metal ??

the ms says 3 mol .... how??

also .... how many moles of NaOH will react with this acid
a) in the cold
b) on heating ??
 
Messages
153
Reaction score
1,433
Points
153
3 mol of H2 are produced because Na will react with the 2 OH on the phenol and the 3 OH on the other ring and also with the OH of the acid group..so u have 6mol of H -----> 3 mol of H2

a) in the cold - 3 mol of NaOH (reacts with the 2 OH on the phenol and the acid group )
b) when heated - 4 mol of NaOH (breaks the ester bond in addition to reacting with the ones above)
 
Messages
887
Reaction score
466
Points
73
View attachment 38934

how many moles of H2 will be produced when 1 mol of this acid reacts with an excess of Na metal ??

the ms says 3 mol .... how??

also .... how many moles of NaOH will react with this acid
a) in the cold
b) on heating ??
well Na reacts with alcohol phenol and carboxylic acid right so given this fact there are 6 hydrogen available to be replaced with Na metal 6 hydrogen atoms. 2 atoms in one molecule so 3 moles .
for (a) alcohols dont react with NaOH so 3 will react
for (b) again 2 OH of phenols and 1 OH of carboxylic acid will react but this time there would also be base hydrolysis so total 4 moles of NaOh required
 
Messages
382
Reaction score
315
Points
73
seondary structure consist of hydrogen bondings being formed between -CO and -NH group
they form either alpha helix of beta plated structures

the tertiary structure consist of 4 types of bondings
1. Hydrogen bonging
2. ionic bond between opositely charged groups
3. van der waals forces between hydrophobic R groups
4. disulphide covalent bridges (-S-S-), it's only formed between cystine molecules, as they are the only ones that have S in them

Primary structure only consist of arengements of aminoacids
Thanks man.. much appreciated
 
Messages
1,394
Reaction score
1,377
Points
173
daredevil 6Astarstudent can anyone help me understand that highlighted text in 3rd file from right well i think it contradicts with the data booklet in 4th file View attachment 38936 View attachment 38937 View attachment 38938 View attachment 38939
this has me beat.... it is contradictory.
at first i thought maybe bcz of OH or benzene ring the value shifted but even OH cant change the value this much...
i really succk big time at nmr..... and i request againn... IF anyone HAS any notes on NMR PLEAAASSEEE post them up and tag me.... thankss.... anything that cud help!!
 
Top