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ALL CIE CHEMISTRY DOUBTS HERE !!
Vin:
Does anybody have notes for mass- spectroscopy?
Like for eg, this question :
A sample of chlorine containing isotopes of mass numbers 35 and 37 was analysed in a
mass-spectrometer.
How many peaks corresponding to Cl2+ were recorded?
A 2 B 3 C 4 D 5
Could anybody fill me in with some sense as to what the ques means in English? and everything in and around this topic? Thanks.
Amii:
--- Quote from: Vin on January 08, 2011, 01:19:54 pm ---Does anybody have notes for mass- spectroscopy?
Like for eg, this question :
A sample of chlorine containing isotopes of mass numbers 35 and 37 was analysed in a
mass-spectrometer.
How many peaks corresponding to Cl2+ were recorded?
A 2 B 3 C 4 D 5
Could anybody fill me in with some sense as to what the ques means in English? and everything in and around this topic? Thanks.
--- End quote ---
ans will be B
1 peak for Cl 35 and Cl 35
1 peak for Cl 35 and Cl 37
1 peak for Cl 37 and Cl 37
I am in a rush - have to get ready for tuitions - I will come back and try to make the explanation proper
Take care :)
Amelia:
Amii is right. :P
This topic is about (M) (M+2) (M+3) peaks. ::)
Both bromine and chlorine naturally occur as mixtures of 2 isotopes, with the relative abundances as shown :-
Chlorine -
35 - Cl relative abundance - 75.8%
37-Cl relative abundance - 22.4%
approximate ratio - 3:1
Bromine -
79 - Br relative abundance - 50.5%
81 - Br relative abundance - 49.5%
approx. ratio - 1:1
The mass spectrum of a compound containing one of these elements should therefore show two molecular ions, one with an m/e value two mass units higher than the other. If the molecule contains two chlorine atome, we should expect to see three molecular ions, at m/e values of M, M+2, M+4. The ratio of the M/M+2 peak should reflect the natural abundances. (i.e 3:1 for chlorine, 1:1 for bromine).
You can just go through this : http://www.chemguide.co.uk/analysis/masspecmenu.html :P
P.S - Sorry, esha. :-X
Amii:
--- Quote from: Amelia on January 08, 2011, 04:15:59 pm ---Amii is right. :P
This topic is about (M) (M+2) (M+3) peaks. ::)
Both bromine and chlorine naturally occur as mixtures of 2 isotopes, with the relative abundances as shown :-
Chlorine -
35 - Cl relative abundance - 75.8%
37-Cl relative abundance - 22.4%
approximate ratio - 3:1
Bromine -
79 - Br relative abundance - 50.5%
81 - Br relative abundance - 49.5%
approx. ratio - 1:1
The mass spectrum of a compound containing one of these elements should therefore show two molecular ions, one with an m/e value two mass units higher than the other. If the molecule contains two chlorine atome, we should expect to see three molecular ions, at m/e values of M, M+2, M+4. The ratio of the M/M+2 peak should reflect the natural abundances. (i.e 3:1 for chlorine, 1:1 for bromine).
You can just go through this : http://www.chemguide.co.uk/analysis/masspecmenu.html :P
P.S - Sorry, esha. :-X
--- End quote ---
LOL why sorry? :-\ :D
Thank you so much ;D
I was getting late so I had to run :P
astarmathsandphysics:
The number of peaks is related to the number of isotopes
chlorine has two isotopes (I think) mass numbers 37 and 36 so Cl2 has three masses
2*37=74, 37+36=73,36+36=72
Hence three peaks, one for each mass
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