Chemistry and Physics some Keypoints/Notepoints (onDemandOnly) !! :)

[littlecloud11]

Thanks for the feedback
well Peaks will be doubled in low resolution NMR they never split in Low resolution NMR
they only split in highResolutuion NMR!

Well you mentioned that under the heading 'peak splitting depends on:' So I assumed you were talking about high resolution.

 

[xhizors]

Well you mentioned that under the heading 'peak splitting depends on:' So I assumed you were talking about high resolution.

Thanks for mentioning ! I edited

 

[PhyZac]

Bismillah,
MashaAllah a BIG question
Ok so i assume you know about Peaks
..........
Hope you get the idea!

Thank you so much,
I have doubt there, when you said split to 6, you meant the CH3??

Jazak Allah khairan, thank you, May Allah S.W.T grant you and your family Jannatul-firdous, and grant you world distinction Aameen.

 

[iKhaled]

Open pg 292

oh this...

you need to know that one mole of electrons carry a charge of 96 500C. so farady unit can be expressed as 96500C/mol. we use this with the equation Q=IT to see the mass of whatever that has been produced on the electrode during electrolysis.

take the first example in the "worked example" we want to calculate the mass of lead that has been deposited at the cathode during electrolysis when a current of 1.5A flows through molten lead bromide for 20min

now always the first step to do is to write the half equation that happens at the electrode of the mass we r trying to find in this question it is lead that has been deposited on the cathode so PB^2 + 2e ---- >Pb the reason we write the half equation is to see how many moles it needs to deposit one mole of pb and remember that one mole of pb has a mass of 207g so now we calculate the charge produced during that 20min

Q= IT a formula we used in physics to calculate the charge remember t is always in second so here we need to convert the 20min into seconds by multiplying it by 60 so 20x60= 1200s

now Q = 1.5 X 1200 = 1800C is produced during that time. now we know that for one mole(207g) of lead to be produced we will have a charge of 96500x2 = 193,000C (that is the charge that the 2 moles carry to produce one mole of pb..we got it from our equation and using farady value) so now

1800 = x grams of pb
193000 = 207 grams of pb do da cross multiplication and u will get x = 1.93g of lead will be produced in 20min with a current of 1.5A

do the next example alone to see if u understood it or not and if not tell me and i will explain too ! and oh yes tell me if u understood this or not

 

[littlecloud11]

Thanks for mentioning ! I edited

Anytime

 

[knowitall10]

oh this...

you need to know that one mole of electrons carry a charge of 96 500C. so farady unit can be expressed as 96500C/mol. we use this with the equation Q=IT to see the mass of whatever that has been produced on the electrode during electrolysis.

take the first example in the "worked example" we want to calculate the mass of lead that has been deposited at the cathode during electrolysis when a current of 1.5A flows through molten lead bromide for 20min

now always the first step to do is to write the half equation that happens at the electrode of the mass we r trying to find in this question it is lead that has been deposited on the cathode so PB^2 + 2e ---- >Pb the reason we write the half equation is to see how many moles it needs to deposit one mole of pb and remember that one mole of pb has a mass of 207g so now we calculate the charge produced during that 20min

Q= IT a formula we used in physics to calculate the charge remember t is always in second so here we need to convert the 20min into seconds by multiplying it by 60 so 20x60= 1200s

now Q = 1.5 X 1200 = 1800C is produced during that time. now we know that for one mole(207g) of lead to be produced we will have a charge of 96500x2 = 193,000C (that is the charge that the 2 moles carry to produce one mole of pb..we got it from our equation and using farady value) so now

1800 = x grams of pb
193000 = 207 grams of pb do da cross multiplication and u will get x = 1.93g of lead will be produced in 20min with a current of 1.5A

do the next example alone to see if u understood it or not and if not tell me and i will explain too ! and oh yes tell me if u understood this or not

MashAllah TabarakAllah It wasn't that i didn't understand it brother-sorry for bothering u- I just wanted a short and clear explaination of this topic.
But Jazak Allahu Khairan Ukhee.
Now i understand the next example too
Thank you very much

 

[seneria]

can anyone explain me how to deduce the structure in NMR? I'm very bad at it... thanks

 

[knowitall10]

Oh wait.. can u please explain the Faraday's constant too? and it's relation with the Avogadro's constant (next page)
Allah Yajzeek
P.s. This one i really dont understand....

 

[knowitall10]

can anyone explain me how to deduce the structure in NMR? I'm very bad at it... thanks

Look at page one Brother xhizors explains it pretty awesomly

 

[xhizors]

Thank you so much,
I have doubt there, when you said split to 6, you meant the CH3??

Jazak Allah khairan, thank you, May Allah S.W.T grant you and your family Jannatul-firdous, and grant you world distinction Aameen.

Ameen Ameen
JazakAllah JazakAllah
yeah CH3 peak will split into 6
so if an NMR is used to inspectate a propane
results:
a)In Low Resolution NMR:
their would be 2 peaks
one peak for Ch3 x2 (as peak will be doubled(ch3-Ch2) and (Ch2-Ch3))
and one for ch2
b) In high Resolution NMR:
one peak splitted into 3(triplet) and doubled in height (this one is for (ch3-Ch2) and (Ch2-Ch3))
and other would be in 7let
(Ch3-Ch2-Ch3) total proton in neighbours 6 +1 = 7 ( using fact n+1 where n = number of total protons in neighbours --Credit goes to littlecloud11 for this fact)
Hope that helps

 

[iKhaled]

MashAllah TabarakAllah It wasn't that i didn't understand it brother-sorry for bothering u- I just wanted a short and clear explaination of this topic.
But Jazak Allahu Khairan Ukhee.
Now i understand the next example too
Thank you very much

oh so did i provide u with a clear explanation or not still? and u r welcomed!

 

[seneria]

Ameen Ameen
JazakAllah JazakAllah
yeah CH3 peak will split into 6
so if an NMR is used to inspectate a propane
results:
a)In Low Resolution NMR:
their would be 2 peaks
one peak for Ch3 x2 (as peak will be doubled(ch3-Ch2) and (Ch2-Ch3))
and one for ch2
b) In high Resolution NMR:
one peak splitted into 3(triplet) and doubled in height (this one is for (ch3-Ch2) and (Ch2-Ch3))
and other would be in 8let
(Ch3-Ch2-Ch3) total proton in neighbours 6 +1 +1 = 8 ( 2 neighbours so 2+ in total Protons)
Hope that helps

I didn't get the high resolution thing

 

[iKhaled]

Oh wait.. can u please explain the Faraday's constant too? and it's relation with the Avogadro's constant (next page)
Allah Yajzeek
P.s. This one i really dont understand....

see u just need to know the formula F = Le where F is the farady constant, L is avogadro's no and e is the charge of one electron. it is used to prove avogadro's no thats it...

 

[xhizors]

Oh wait.. can u please explain the Faraday's constant too? and it's relation with the Avogadro's constant (next page)
Allah Yajzeek
P.s. This one i really dont understand....

F=Le
L=Avagadro no = 6.02x10^23
e=Charge ~ 1.6x10^-19
u get approx 96500 C/mol i guess

 

[xhizors]

I didn't get the high resolution thing

Bismillah,
MashaAllah a BIG question
Ok so i assume you know about Peaks
we can deduce the structure by high resolution NMR where the peaks are splits apart
Peaks Splitting Depends on(highResolution NMR):
the proton environment in the neighbour (lol not in my neighbour)
the one which carbon is attatched to specifically
the pattern of splitting is: number of H atoms in neighbour +1
so assume fragment of CH3 is detected and it is attatched to Ch2 and on other side with ch2
so the split is breaking in 6let(6peaks)
Condition:
if Ch3 is attatched to most electronegative environment like Ch3-OH
then ch3 peak wont be splitting
ok so quest:
if its like ch3-ch2-OH how many peaks if so and how'll they split

now by neighbourhood u can get an idea of Hydrogens etc
Nmr Peaks x-axis is Chemical Shifts Values
so after judging what could possibly be around from peaks u pick a data booklet and match your prediction by Chemical shift values

Hope you get the idea!

now tell me where you have confusion

 

[PhyZac]

Ameen Ameen
JazakAllah JazakAllah
.........
(Ch3-Ch2-Ch3) total proton in neighbours 6 +1 +1 = 8 ( 2 neighbours so 2+ in total Protons)
Hope that helps

Wa eyyakum.

Thank you again, but very sorry, I am confused in one thing,
where did you get 6 + 1 + 1??

JazakAllah khiaran, May Allah S.W.T reward you for all your help, Aameen.

 

[littlecloud11]

(Ch3-Ch2-Ch3) total proton in neighbours 6 +1 +1 = 8 ( 2 neighbours so 2+ in total Protons)
Hope that helps

Is this 8-split peak for -CH2-?

 

[xhizors]

Wa eyyakum.

Thank you again, but very sorry, I am confused in one thing,
where did you get 6 + 1 + 1??

JazakAllah khiaran, May Allah S.W.T reward you for all your help, Aameen.

Ch2 have two neighbours with awesome protons(specifically Hydrogen Atoms) each 3
so from both neighbours you get 6 protons
now as we know that when we split we apply fact (n+1) where n is the proton in "a" neighbour
so we have 2 neigbours so add 2 in 6 you get 8 splits

 

[xhizors]

Is this 8-split peak for -CH2-?

yup!

 

[PhyZac]

Ch2 have two neighbours with awesome protons(specifically Hydrogen Atoms) each 3
so from both neighbours you get 6 protons
now as we know that when we split we apply fact (n+1) where n is the proton in "a" neighbour
so we have 2 neigbours so add 2 in 6 you get 8 splits

Ooooh, you meant by 6 + 1 + 1 the 8 splits. I thought something else. P.S :Not awesome protons, headache!

Anyway, I now got all what you have said, JazakAllah khairan. Thanks alot!

May Allah S.W.T help and guide you and your family to follow the steps of our beloved Prophet allahi assalatu wa salam. And In Sha Allah, you will be granted with the world distinction.