The mass spectrometer
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I would recommend watching this video if you are finding mass spectrometry difficult
https://www.youtube.com/watch?v=5NnYwlDp6vQ
What is the symbol for relative atomic mass?
Ar
What is the symbol for relative molecular mass?
Mr
How do you work out relative atomic mass?
Average mass of 1 atom/ 1/12 mass of 1 atom of 12C
How do you work out relative molecular mass?
Average mass of molecule/ 1/12 mass of 1 atom of 12C
When are mass spectrometers used in everyday life?
Forensic scientists use them to identify substances (such as illega drugs).
What does the mass spectrometer do?
Determines the mass of seperate atoms
What is the name of the mass spectrometer that we have to know?
time of flight mass spectronomy (TOF).
Draw a diagram of the TOF mass spectrometer
What are the 6 steps inside a mass spectrometer?
• Vacuum • Ionisation • Acceleration • Ion drift • Detection • Data analysis (Very Ignorant Alligators Imagine Dinosaurs Dancing)
What happens inside a vacuum of a mass spectrometer?
The whole machine is kept under a vacuum in order to prevent the ions from colliding with molecules from the air.
What is the ionisation step?
The atom or molecule is ionised by knocking one or more electrons off to give a positive ion.
What is produced after the ionisation stage (after the solution is past through the hollow needle)?
Tiny positively charged droplets which have lost electrons to the positive charge of the supply.
Which ions move faster towards the negative plate?
Lighter ions and more highly charged ions move at greater speed towards the nagative plate.
What happens in the ion drift stage?
The ions pass through a hole in the nagatively charged plate which forms a beam. This beam travels along a tube (called the flight tube) to the detector.
What happens at the detections stage?
When ions with the same charge arrive at the detector the flight times are recorded via the positive ions picking up an electron from the detector which causes a current to flow.
What happens at the data anyalysis stage?
The signal from the detector is passed to a computer which generates a mass spectrum.
Draw the axis of a mass spectrum graph
How many decimal places does low resolution mass spectrometry measure to?
1 decimal place
How many decimal places does high resolution mass spectrometry measure to?
5 decimal places