Charges of ions in a mass spectrometer

Click For Summary
SUMMARY

The discussion focuses on calculating the charge of 126C ions in a mass spectrometer using the formula F=qvB=mv²/r. The ions, with a speed of 5.67 x 10^4 m/s and a magnetic field strength of 3.2 x 10^-2 T, yield a charge of 3.2 x 10^-19 C, equivalent to 2e. A point of confusion arises regarding the mass used in the calculation, as the mass of a 126C atom is approximately 1.99264654 x 10^-26 kg, leading to questions about the initial value of 14 atomic units used in the solution.

PREREQUISITES
  • Understanding of mass spectrometry principles
  • Familiarity with the Lorentz force equation
  • Knowledge of atomic mass units and conversions
  • Basic proficiency in algebra and physics calculations
NEXT STEPS
  • Review the Lorentz force and its application in mass spectrometry
  • Learn about the relationship between charge, mass, and velocity in charged particles
  • Investigate the significance of atomic mass units in physical chemistry
  • Explore the impact of magnetic field strength on ion deflection in mass spectrometers
USEFUL FOR

This discussion is beneficial for physics students, particularly those studying mass spectrometry, as well as educators and professionals involved in analytical chemistry and instrumentation.

Karagoz
Messages
51
Reaction score
5

Homework Statement


In a mass spectrometer, a few 126C ions are deflected with a radius of 12.9 cm. The ions have a speed of 5.67*10^4 m/s when they enter the field. The magnetic field has a strength of 3.2*10^-2 T. The charge of these ions must be ...

SOLUTION:
We use the formula: i F=qvB = mv2/r and find q.

q= mv / rB = (14*1,66·10^-27 kg * 5,67*10^4 m/s) / (0,129m * 3,2*10^-2 T) = 3,2*10^-19 C = 2e

Homework Equations



One atomic unit is 1,66*10^-27 kg

But isn't the mass of 126C atom is ca 1.99264654*10^-26 kg, which is ca 12 atomic units? ( https://www.britannica.com/science/atomic-mass )

Where does the 14 come from in the solution?

The Attempt at a Solution

 
Physics news on Phys.org
Perhaps the question was modified from Nitrogen atoms to Carbon atoms at some point but the solution was not updated to reflect this?
 
  • Like
Likes   Reactions: drvrm

Similar threads

Mass spectrometer with a Lead element
  • · Replies 40 ·
2
Replies
40
Views
5K
Mass spectrometer problem -- Need help
  • · Replies 3 ·
Replies
3
Views
2K
How Is Current Calculated in a Mass Spectrometer?
  • · Replies 3 ·
Replies
3
Views
2K
Speed, force, magnetic flux of an ion?
  • · Replies 13 ·
Replies
13
Views
3K
Mass-to-Charge Ratio of an Ion in Mass Spectrometer
  • · Replies 1 ·
Replies
1
Views
2K
TOF (mass spectrometer) Analyzer Question
  • · Replies 2 ·
Replies
2
Views
2K
Distance between Isotopes in a mass spec
  • · Replies 8 ·
Replies
8
Views
10K
Circular Motion in a Simple Mass Spectrometer
  • · Replies 4 ·
Replies
4
Views
5K
Magnesium ion entering a mass spectrometer. find r
  • · Replies 1 ·
Replies
1
Views
4K
With what speed does the ion enter the magnetic field in a mass spectrometer?
  • · Replies 10 ·
Replies
10
Views
4K