# chem help PLEASE ANY WHO DID AS CHEM LAST YEARWatch

#1
this was a question on the chemistry paper last year
it basically says bromine has two isotopes 79Br and 81Br (thats eighty one NOT eighty seven) in approximately equal abundance. in A TOF mass spec bromine forms ion w formal (Br2)+.
sketch the pattern of peaks u would expect to see in the mass speed of a sample of bromine.
it has abundance on y axis 0-100%
then m/z on x axis 156-164

THANK YOU XX
0
1 year ago
#2
(Original post by Jollyjules1320)
this was a question on the chemistry paper last year
it basically says bromine has two isotopes 79Br and 81Br (thats eighty one NOT eighty seven) in approximately equal abundance. in A TOF mass spec bromine forms ion w formal (Br2)+.
sketch the pattern of peaks u would expect to see in the mass speed of a sample of bromine.
it has abundance on y axis 0-100%
then m/z on x axis 156-164

THANK YOU XX
Ok, so basically as bromine exists as Br2 as it is a diatomic molecule. Start off with 79Br. Multiply 79 by two (for the two bromine atoms) to give you 158. There will be a peak here at m/z of 158.

For 81Br, multiply the 81 by two (for the two bromine atoms) to give you 162. There will be another peak here at m/z of 162.

The question seems to be a bit vague as to what the abundance would be for each peak. Was there no ratio given for abundance of each Br isotope?
0
1 year ago
#3
(Original post by Hajra Momoniat)
Ok, so basically as bromine exists as Br2 as it is a diatomic molecule. Start off with 79Br. Multiply 79 by two (for the two bromine atoms) to give you 158. There will be a peak here at m/z of 158.

For 81Br, multiply the 81 by two (for the two bromine atoms) to give you 162. There will be another peak here at m/z of 162.

The question seems to be a bit vague as to what the abundance would be for each peak. Was there no ratio given for abundance of each Br isotope?

(Original post by Jollyjules1320)
it basically says bromine has two isotopes 79Br and 81Br (thats eighty one NOT eighty seven) in approximately equal abundance
..
0
#4
(Original post by Hajra Momoniat)
Ok, so basically as bromine exists as Br2 as it is a diatomic molecule. Start off with 79Br. Multiply 79 by two (for the two bromine atoms) to give you 158. There will be a peak here at m/z of 158.

For 81Br, multiply the 81 by two (for the two bromine atoms) to give you 162. There will be another peak here at m/z of 162.

The question seems to be a bit vague as to what the abundance would be for each peak. Was there no ratio given for abundance of each Br isotope?
no, they just said that they are in approximately equal abundance
0
1 year ago
#5
(Original post by Jollyjules1320)
no, they just said that they are in approximately equal abundance
Well... that gives you the ratio...
0
1 year ago
#6
(Original post by Jollyjules1320)
this was a question on the chemistry paper last year
it basically says bromine has two isotopes 79Br and 81Br (thats eighty one NOT eighty seven) in approximately equal abundance. in A TOF mass spec bromine forms ion w formal (Br2)+.
sketch the pattern of peaks u would expect to see in the mass speed of a sample of bromine.
it has abundance on y axis 0-100%
then m/z on x axis 156-164

THANK YOU XX
You could have:

Br79 - Br 79 = 158
Br79 - Br81 = 160
Br81-Br79 = 160
Br81 - Br81 = 162

So 3 peaks.
0
#7
(Original post by LT83)
You could have:

Br79 - Br 79 = 158
Br79 - Br81 = 160
Br81-Br79 = 160
Br81 - Br81 = 162

So 3 peaks.
thank you! how would you work out the ratio?
0
5 months ago
#8
(Original post by Jollyjules1320)
thank you! how would you work out the ratio?
(Original post by LT83)
You could have:

Br79 - Br 79 = 158
Br79 - Br81 = 160
Br81-Br79 = 160
Br81 - Br81 = 162

So 3 peaks.
I know I'm like a year later but where did 3 peaks come from? If it has two isotopes?
0
5 days ago
#9
79 79= 15881 81=162 79 81 = 160 81 79 = 160 160 occurs twice , 2/4 times = 508 occurs 1/4 times = 25% 162 occurs 1/4 times = 25% This will make more sense if you do a 81 and 79 grid to give you 4 answers
0
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