HELP chemistry edexcel question As level

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Bliss_
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a sample of Oxygen contains the isotopes 16O 17O 18O
how many peakss would be there for the O2+IONS in the mass spectrum of this sample of oxygen?
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Dowel
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3 because each isotope has a 1+ ion and those are (for now) the only ions created in the mass spectrometer
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Bliss_
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(Original post by Dowel)
3 because each isotope has a 1+ ion and those are (for now) the only ions created in the mass spectrometer
unfortunately the answer is 5
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Sunethra
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(Original post by RAZA1999)
unfortunately the answer is 5
There are five peaks cause due to 18, 16, 32,34,36
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Dowel
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(Original post by RAZA1999)
unfortunately the answer is 5
Yeah sorry about that :P

Its due to each isotope (in diatomic form) losing one electron and then also when you get all of the different possible combinations of the three so in the spectrometer you have O2(32) O2(34) O2(36) O2(35) and O2(33) and when each lose an electron you get those specific positive O2 positive ions.

I think this is right, I misread it the first time i thought it just said O+ ions
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Bliss_
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(Original post by Sunethra)
There are five peaks cause due to 18, 16, 32,34,36
why did you ignore O17
i dont get it
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Bliss_
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(Original post by Dowel)
Yeah sorry about that :P

Its due to each isotope (in diatomic form) losing one electron and then also when you get all of the different possible combinations of the three so in the spectrometer you have O2(32) O2(34) O2(36) O2(35) and O2(33) and when each lose an electron you get those specific positive O2 positive ions.

I think this is right, I misread it the first time i thought it just said O+ ions
can you please explain how you did it?
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Dowel
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(Original post by RAZA1999)
can you please explain how you did it?
Ok so from O(17) O(18) and O(16) you need to work out how many diatomic forms of oxygen can be created. So you can get O2 made up of two O(16) atoms to form O2(32) and another made up of O(17) atoms to form O2(34) and another made up of two (O18) atoms to form O2(36).

So now we have O2(32) O2(34) and O2(36)
you can also combine different isotopes of oxygen to get a diatomic molecule:
so combine O(17) with O(18) you get O2(35)
and combine O(16) with O(17) you get O2(33)
but if we combine O(16) with O(18) you get O2(34) which is the same as a previous combination and so we discard it

So you end up with O2(34) O2(32) O2(36) O2(35) and O2(33) and all of these form positive (1+) molecules when ionised
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Bliss_
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(Original post by Dowel)
Ok so from O(17) O(18) and O(16) you need to work out how many diatomic forms of oxygen can be created. So you can get O2 made up of two O(16) atoms to form O2(32) and another made up of O(17) atoms to form O2(34) and another made up of two (O18) atoms to form O2(36).

So now we have O2(32) O2(34) and O2(36)
you can also combine different isotopes of oxygen to get a diatomic molecule:
so combine O(17) with O(18) you get O2(35)
and combine O(16) with O(17) you get O2(33)
but if we combine O(16) with O(18) you get O2(34) which is the same as a previous combination and so we discard it

So you end up with O2(34) O2(32) O2(36) O2(35) and O2(33) and all of these form positive (1+) molecules when ionised
oh, alright. Thank you loads mate.
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Ella blinx
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Thanks, the answers helps but it doesn't have my exact answers.
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BobbJo
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#11
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(Original post by Ella blinx)
Thanks, the answers helps but it doesn't have my exact answers.
What do you mean? There are exactly 5 peaks
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bhattibaadshah
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#12
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what if there's a question with the charge on O2 as 2 ?
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shevinBLZ
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#13
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thanks alottt for the answer
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