A sample containing ¹²C, 16O, and an unknown isotope is analyzed in a mass spectrometer. As in Fig. 19.17(a), the ions move around a semicircle before striking a photographic plate. The ¹²C⁺ and ¹⁶O⁺ ions are separated by 2.250 cm on the plate, and the unknown isotope strikes the plate 1.160 cm from the ¹²C⁺ ions. What is the mass of the unknown element?

In each of these problems, the ions entering the mass spectrometer have the same charges. Except in Problem 30, the ions enter the magnetic field with equal kinetic energies (not equal speeds). Use these atomic mass values: ¹²C, 12.00 u; ¹⁴C, 14.00 u; ¹⁶O, 15.99 u. The conversion between atomic mass units and kilograms is 1 u = 1.66 × 10⁻²⁷ kg.

Transcribed Image Text:

Ion source Low-speed ions Ions all have same KE AV Accelerating potential (a) Photographic plate or other detector Uniform B between poles of magnet e 0 Ⓒ e 0 0 0 O 0 O O -Ion beam Detector (b) Magnet Slit Recorder