# Mass Spectrometry question helpWatch

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#1
Hi,

I'm studying AS OCR chemistry and I'm not sure how to answer one of the questions on Mass Spectrometry.

Question: A sample of Hydrogen containing the Isotopes Hydrogen-1, Hydrogen-2 and Hydrogen-3 was analysed in a Mass Spectrometer. How many peaks corresponding to H2+ would be expected?

The answer is 5 but I have no idea how/why that is the answer.

Any help would be appreciated
0
3 years ago
#2
(Original post by -inspired-)
Hi,

I'm studying AS OCR chemistry and I'm not sure how to answer one of the questions on Mass Spectrometry.

Question: A sample of Hydrogen containing the Isotopes Hydrogen-1, Hydrogen-2 and Hydrogen-3 was analysed in a Mass Spectrometer. How many peaks corresponding to H2+ would be expected?

The answer is 5 but I have no idea how/why that is the answer.

Any help would be appreciated
In a molecule there are two atoms and either of the atoms can be 1H, 2H or 3H

How many possible combinations are there?
0
#3
(Original post by charco)
In a molecule there are two atoms and either of the atoms can be 1H, 2H or 3H

How many possible combinations are there?
I thought of that, but wouldn't that only provide three combinations?

1H + 2H
1H + 3H
2H + 3H

Unless I'm missing something (which is highly likely!)
0
3 years ago
#4
(Original post by -inspired-)
I thought of that, but wouldn't that only provide three combinations?

1H + 2H
1H + 3H
2H + 3H

Unless I'm missing something (which is highly likely!)
What about 1H + 1H, 2H + 2H and 3H + 3H?
0
#5
(Original post by charco)
What about 1H + 1H, 2H + 2H and 3H + 3H?
Ah I knew I was forgetting some combinations! Wouldn't that make six peaks though?
0
3 years ago
#6
What would the m/z values of the six peaks be?
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#7
(Original post by Pigster)
What would the m/z values of the six peaks be?
Oh I see, so the 1H + 3H possibility has the same m/z value as 2H + 2H so wouldn't form it's own peak so there would be five. Thank you so much both of you
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