Chemistry: Mass Spectrometer

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  • Created by: Shanice_D
  • Created on: 11-09-14 20:49
What does the mass spectrometer do?
A mass spectrometer produces charged particles (ions) from the chemical substances that are to be analyzed. The mass spectrometer then uses electric and magnetic fields to measure the mass (weigh") of the charged particles.
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What happens in the mass spectrometer?
-The atoms are turned into ions -They are then accelerated -Then deflected according to their masses & charges -Arrive at the detector
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Why is the instrument kept under a high vacuum?
So that the ions don't collide with air molecules which might stop them reaching the detector
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What happens in the ionisation stage in the mass spectrometer?
A beam of electrons from an electron gun knocks out electrons from atoms/molecules of the sample to form positive ions. Nearly all the atoms/molecules lose 1 electron & form ions with 1+ charge but smaller numbers lose 2 electrons to form ions with 2
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What happens in the acceleration stage in the mass spectrometer?
The positive ions attract towards the negatively charged plates & are accelerated to a high speed. The speed depends on their mass (lighter the mass, faster they go.) Some ions pass through slits in plates that form ions into beams
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What happens in the deflection stage in the mass spectrometer?
The beams of ions move into the magnetic field at right angles to its direction of travel. The magnetic field deflects the beam of ions into an arc of a circle
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What does the deflection of an ion depend on?
On the ratio of its mass to charge (heavier ions are deflected less, 2+ ions deflected twice as much as 1+ ions with the same mass) -Magnetic field strength (the stronger the field, the greater the deflection)
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What happens in the detection stage in the mass spectrometer?
The magnetic field gradually increases so ions of increasing mass enter the detector one after another. Ions strike the detector, accept electrons, lose charge & create currents
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Other cards in this set

Card 2

Front

What happens in the mass spectrometer?

Back

-The atoms are turned into ions -They are then accelerated -Then deflected according to their masses & charges -Arrive at the detector

Card 3

Front

Why is the instrument kept under a high vacuum?

Back

Preview of the front of card 3

Card 4

Front

What happens in the ionisation stage in the mass spectrometer?

Back

Preview of the front of card 4

Card 5

Front

What happens in the acceleration stage in the mass spectrometer?

Back

Preview of the front of card 5
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