Mass spectrometry of elements Original Scenario-Based Practice

Questions

1. 1.

   An autonomous exploration probe extracts a vaporized elemental sample from an asteroid and analyzes it using a magnetic-deflection mass spectrometer. In the primary scan, singly charged ions ($M^+$) of two isotopes produce sharp peaks at $m/z = 60$ and $m/z = 64$. If an unexpected high-voltage discharge in the ionization chamber causes all atoms of this element to form doubly charged ions ($M^{2+}$) instead, which statement correctly predicts the resulting mass spectrum?

   • A) The peaks will appear at $m/z = 30$ and $m/z = 32$ because halving the mass-to-charge ratio causes the ions to experience greater curvature in the magnetic field.
   • B) The peaks will appear at $m/z = 120$ and $m/z = 128$ because doubling the ionic charge doubles the effective mass registered by the magnetic detector.
   • C) The peaks will remain at $m/z = 60$ and $m/z = 64$ because the mass spectrometer measures isotopic mass independently of ionic charge.
   • D) A single merged peak will appear at $m/z = 62$ because the higher electrostatic charge fuses the flight paths of the two isotopes.

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