AQA A-Level Chemistry 7405
Atomic Structure
Amount of Substance
Bonding
Energetics and Thermodynamics
Kinetics
Chemical Equilibria
Redox and Electrochemistry
Acids and Bases
Periodicity and Group Chemistry
Period 3 Elements and Their Oxides
Transition Metals
Introduction to Organic Chemistry
Hydrocarbons
Halogenoalkanes, Alcohols and Organic Analysis
Carbonyls, Carboxylic Acids and Derivatives
Aromatic Chemistry and Amines
Polymers, Amino Acids, Proteins and DNA
Organic Synthesis, NMR and Chromatography
Atomic Structure
Time of Flight Mass Spectrometry: Drift, Detection and Calculating m/z
- 3 things to know
- Papers 1 and 3
Overview
Why heavier ions drift more slowly, what happens at the detector, and getting relative atomic mass from the spectrum.
What you need to know
Answer each one before you reveal it.
Why do ions with different masses separate during the drift stage?
What happens at the detector in the fourth stage of TOF mass spectrometry?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What happens during the third stage of TOF mass spectrometry?
Model answer
Ions drift through a flight tube (field-free region) and separate according to their mass to charge ratio
- 2
Why do ions with different masses separate during the drift stage?
Model answer
Lighter ions travel faster than heavier ions (at the same kinetic energy), so they reach the detector first
- 3
What happens at the detector in the fourth stage of TOF mass spectrometry?
Model answer
Ions are detected and the time of flight is recorded, which is used to calculate the m/z ratio
- 4
How is the time of flight related to the mass to charge ratio of an ion?
Model answer
Ions with smaller m/z ratios have shorter flight times; ions with larger m/z ratios have longer flight times
- 5
What equation relates kinetic energy to mass and velocity?
Model answer
KE = ½mv²
- 6
Starting from KE = ½mv², how can you derive an expression for velocity in terms of kinetic energy and mass?
Model answer
v = √(2KE/m)
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