Ch.2 - Atoms, Molecules & Ions

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.2 - Atoms, Molecules & Ions

Problem 130b

Chapter 2, Problem 130b

Refer to Figure 2.10 showing a schematic illustration of a mass spectrometer. (b) Compare two ions with a +1 charge traveling through the curved, evacuated tube in the mass spectrometer. Will a heavier ion or lighter ion be deflected to a greater degree by the magnetic field?

Verified step by step guidance

Understand that a mass spectrometer is a device used to separate ions based on their mass-to-charge ratio (m/z).

Recognize that ions with the same charge but different masses will experience different degrees of deflection when subjected to a magnetic field.

Recall that the force exerted by the magnetic field on a charged particle is given by the equation: \( F = qvB \), where \( q \) is the charge, \( v \) is the velocity, and \( B \) is the magnetic field strength.

Note that the radius of curvature \( r \) of the ion's path in the magnetic field is given by \( r = \frac{mv}{qB} \), where \( m \) is the mass of the ion.

Conclude that for ions with the same charge, a heavier ion (larger \( m \)) will have a larger radius of curvature and thus be deflected less than a lighter ion.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Mass Spectrometry

Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio of ions. In this process, ions are generated, accelerated, and then passed through a magnetic field, where their paths are influenced by their mass and charge. This allows for the identification and quantification of different ions based on their mass.

Lorentz Force

The Lorentz force is the force experienced by a charged particle moving through a magnetic field. It is perpendicular to both the velocity of the particle and the direction of the magnetic field. The magnitude of the deflection of an ion in a magnetic field is influenced by its mass and charge, with lighter ions experiencing greater deflection than heavier ions.

Ion Deflection in Magnetic Fields

In a magnetic field, ions with different masses and charges will follow different trajectories. Lighter ions, having less mass, are deflected more than heavier ions when subjected to the same magnetic field strength. This principle is crucial for separating ions based on their mass-to-charge ratios in mass spectrometry.

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