# Finding the relative atomic mass with no data values on the mass spectrumWatch

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Thread starter 3 weeks ago
#1
How do you do this?

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3 weeks ago
#2
With occult methods? Seems like an editing error, but I'll tag Pigster and MexicanKeith in case I'm missing something.
Last edited by Tolgarda; 3 weeks ago
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3 weeks ago
#3
(Original post by Mad Man)
How do you do this?

Yeah...without any numbers on the axes that's going to be impossible...
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3 weeks ago
#4
(Original post by Mad Man)
How do you do this?

84.1 - Krypton.

How did I do it?

It is a secret.

Take that @MexicanKeith (yes I don't know how to do one of those link things).
Last edited by Pigster; 3 weeks ago
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3 weeks ago
#5
(Original post by Pigster)
84.1 - Krypton.

How did I do it?

It is a secret.

Take that @MexicanKeith (yes I don't know how to do one of those link things).
This is surely witchcraft!
I think you're right, but from the original question you can't work it out...surely
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3 weeks ago
#6
(Original post by MexicanKeith)
This is surely witchcraft!
I think you're right, but from the original question you can't work it out...surely
Hey, I said it is a secret!

Oh well, you've twisted my arm...

Being a gas (I assumed at RTP) narrows it down to 11 elements.

Given the four peaks, it couldn't be a diatomic (e.g. Cl2 has peaks at 70, 71 and 72 and you know about the peak heights). Which meant it was a noble gas.

He doesn't have 4 isotopes, not stable ones anyhoo. A vague memory told me that Ne or Ar don't have four either. So my educated guess led me to Kr or Xe.

A quick google later showed that Kr has: 82Kr, 11.59%; 83Kr 11.50%; 84Kr 56.9%; 86Kr 17.28%, which nicely fits the peak heights in the Q of 1 :1 :6 :2.

Shazam.
Last edited by Pigster; 3 weeks ago
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3 weeks ago
#7
In case you have another question

Question 1) Calculate relative abundance.
Each bar (each isotope) has an m/z value and percentage abundance. Times the m/z value of each isotope with its corresponding percentage abundance (divinde this percentage by 100 si the value is a decimal). Add all values of isotopes together to give you the answer.
Eg. Relative atomic mass of chlorine. Chlorine has two isotopes: 35Cl, 75% and 37Cl, 25%
so, (35 x 0.75) + (37 x 0.25)= 35.5

Question 2) Find the elemt
Look at the periodic table and look at the mass of the element not the proton number/atomic number (They are different)
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3 weeks ago
#8
(Original post by Pigster)
Hey, I said it is a secret!

Oh well, you've twisted my arm...

Being a gas (I assumed at RTP) narrows it down to 11 elements.

Given the four peaks, it couldn't be a diatomic (e.g. Cl2 has peaks at 70, 71 and 72 and you know about the peak heights). Which meant it was a noble gas.

He doesn't have 4 isotopes, not stable ones anyhoo. A vague memory told me that Ne or Ar don't have four either. So my educated guess led me to Kr or Xe.

A quick google later showed that Kr has: 82Kr, 11.59%; 83Kr 11.50%; 84Kr 56.9%; 86Kr 17.28%, which nicely fits the peak heights in the Q of 1 :1 :6 :2.

Shazam.
Witchcraft, as I suspected
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3 weeks ago
#9
(Original post by MexicanKeith)
Witchcraft, as I suspected
"Can we burn her?"
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reply
3 weeks ago
#10
(Original post by Pigster)
Hey, I said it is a secret!

Oh well, you've twisted my arm...

Being a gas (I assumed at RTP) narrows it down to 11 elements.

Given the four peaks, it couldn't be a diatomic (e.g. Cl2 has peaks at 70, 71 and 72 and you know about the peak heights). Which meant it was a noble gas.

He doesn't have 4 isotopes, not stable ones anyhoo. A vague memory told me that Ne or Ar don't have four either. So my educated guess led me to Kr or Xe.

A quick google later showed that Kr has: 82Kr, 11.59%; 83Kr 11.50%; 84Kr 56.9%; 86Kr 17.28%, which nicely fits the peak heights in the Q of 1 :1 :6 :2.

Shazam.
A Level chemistry is something else!
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3 weeks ago
#11
(Original post by Tolgarda)
A Level chemistry is something else!
I couldn't have done it without Google. There must have been more information earlier in the Q, otherwise it would have been impossible.
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Thread starter 3 weeks ago
#12
Thank you.
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3 weeks ago
#13
(Original post by Pigster)
"Can we burn her?"
Only if she weighs the same as a duck
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