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Relative molecular mass help

I’m not sure how to find the relative molecular mass here , can someone explain please6ED51F05-DE09-4352-9479-BC2592D8695D.jpeg
(edited 1 year ago)
It is just the second to the last reading, so in this case it would be 485.1.

It is only 1 mark, so no working out will be necessary.

The very end of this guide from AQA is helpful for this question:
https://filestore.aqa.org.uk/resources/chemistry/AQA-7404-7405-SG-TOFMS.PDF
Original post by hoyam
I’m not sure how to find the relative molecular mass here , can someone explain please6ED51F05-DE09-4352-9479-BC2592D8695D.jpeg

Be careful! With electrospray ionisation you need to subtract one mass unit to account for the H+ added at ionisation. So the actual Mr is 485.1 -1= 484.1
The smaller peak at 486.1 is due to the presence of small amounts of hydrogen and carbon isotopes e.g. carbon-13
Oh yes. Forgot about that in my answer. The attached AQA guide explains.
Reply 4
thank you very much!!!

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