How can I identify the molecular fomula, based on an m/z of 350.7897?

[bellum]

TL;DR Summary: I have the aforementioned m/z and a mass spec graph, my lecturer completely glossed over how to find the molecular formula so I'm stumped.

I have a mass spec with 4 peaks and the m/z value, how can I find the molecular formula.

 

[bellum]

 

[PhysicsEnjoyer31415]

Maybe this can help you

 

[Mayhem]

You have a very exact mass. Use www.chemcalc.org to find possible structures. Remember the nitrogen rule. Deduce possible structures and look if their fragmentation patterns fit the other m/z tops.

 

[DrJohn]

What do you think the highest mass ion represents (in most examples for students to solve, that is).
What do you think the difference between two peaks represents?
What group of atoms could that be?
Repeat for several of the fragment losses.
Build the molecule.