1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

TOF (mass spectrometer) Analyzer Question

  1. Nov 9, 2014 #1
    1. The problem statement, all variables and given/known data

    An unknown hydrocarbon ion required 9.415*10^-6 seconds to travel through the 0.250 T magnetic field of a mass spectrometer with a radius of curvature of 14.1 cm. Since the magnetic chamber is shaped like a 'D' it only travels half way around the circle.

    a. find the speed of the ion through the magnetic field
    b. identity of the ion using the charge to mass ratio (q/m)



    2. Relevant equations

    Fm = qvB
    Fm=Fnet=Fc
    qvB=mv^2/r
    Fc=(4π^2/T^2)

    Unknown variables: q (charge), m (mass), v (velocity) or V (voltage)



    3. The attempt at a solution

    a. Rearranging the formula gives me v=qBr/m. I do not have the (q/m) ratio, so that creates two unknown variables. Next, I tried substituting (4π^2/T^2) as an equivalent for qvB.


    The Fm is 4.453680806*10^11 N.

    After this step I am stuck.


    ANSWER FROM THE BOOK:
    The velocity is 4.7*10^4 m/s, and the substance is pentane, with a (q/m) ratio of 1.34*10^6.
     
  2. jcsd
  3. Nov 9, 2014 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    You can calculate the curve length the ion travels in the spectrometer, and you know the time. That allows to get the speed.
    Afterwards you can find q/m.
     
  4. Nov 9, 2014 #3
    WOW THANKS. I didn't even know it was that simple!! thanks again! :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: TOF (mass spectrometer) Analyzer Question
Loading...