Download Mass Spectrometer Worksheet

The Mass Spectrometer:
Use:
Diagram of apparatus:
Sample calculation:
Doubly charged ions of mass 4.80 x 10-26 kg pass undeflected through the velocity
selection chamber of a mass spectrometer. The velocity selector has an electric field of
3.80 x 105 V/m and a magnetic field of 0.950 T. After leaving the velocity selector the
ions enter the ion separation region and are deflected by a different magnetic field. The
radius of curvature of the ions is 6.00 x 10-2 m, what is the magnetic field strength in the
separation region.
Problems:
1. A positively charged ion (q = 1.60 x 10-19 C) was accelerated from rest through a
potential difference of 1.66 x 104 V. This ion now enters a region where there is a
magnetic field (B = 3.20 x 10-2 T) that is perpendicular to the direction of its motion.
If the magnetic force on the ion is 5.27 x 10-15 N, what is the mass of the ion?
2.
Ans: m = 5.01 x 10-27 kg
Singly charged ions pass undeflected though the velocity selector of a mass
spectrometer. This velocity selector has a magnetic field (B = 2.50 x 10-1 T) and an
electric field (E = 7.00 x 103 V/m) perpendicular to each other. These ions now enter
the separation region where the magnetic field is the same as the velocity selector. If
the radius of the deflected ions is 8.12 x 10-3 m, what is the mass of each ion?
Ans: m = 1.16 x 10-26 kg
3.
A singly charged Li – 7 ion (mass = 1.16 x 10-26 kg) is accelerated from rest through
a potential difference of 4.00 x 104 V. This ion then enters a magnetic field (B =
0.700 T) perpendicular to it. What is the radius of the defected ion?
Ans: r = 1.09 x 10-1 m
4.
A singly charged carbon ion travels in a circular path(r = 11.3 cm) through the ion
separation region of a mass spectrometer. If the velocity selector is composed of an
electric field (E= 7.50 x 104 N/C) and a magnetic field (B = 0.300 T) perpendicular
to each other, what is the mas number of the carbon isotope? (Assume the ion
separation region also has a magnetic field of 0.300 T).
Ans: 13
5.
Doubly charged neon atoms are accelerated from rest through a potential difference
of 2.00 x 103 V. They enter a perpendicular magnetic field (B = 0.200 T) and move
in a circular path with a radius of 10.2 cm. What is the mass of the neon ion?
Ans: m = 3.33 x 10-26 kg
6.
A beam of Pb2+ ions (mass = 3.44 x 10-25 kg) travel through the velocity selector of a
mass spectrometer at a velocity of 5.00 x 104 m/s. What magnetic field strength is
required in the separation region to cause these ions to travel in a circular path with a
radius of 19.6 cm?
Ans: B = 0.274 T