Mass Spectroscopy Flashcards
What is mass Spectroscopy?
A method of identity unknown compounds
What is the main use of mass spectroscopy?
Identifying unknown compounds
What are some uses of mass spectroscopy?
~ identifying unknown compounds
~detecting banned substances such as steroids in athletes
~determining the abundance of an isotope of an atom
How many stages are there in mass spectrometry?
4
What happens during the ionisation stage of mass spectrometry?
- A sample of an element is vaporised and injected into the mass spectrometer, where a high voltage is passed over the chamber.
- High energy electrons are then fired at the element, resulting in the loss of an electron/s and a positive ion being formed.
What happens during the Acceleration stage of mass spectrometry?
- ## Positively charged ions are accelerated towards a negatively charged detection plate.
What causes the defelction of ions in mass spectrometry?
The presence of a magnetic field
What happens during the Ion Drift stage of Mass Spectrometry?
-The ions are deflected by a magnetic field into a curved path.
- The radius of the path is dependent on the charge and the mass of the ion.
What happens during the Detection Stage of Mass Spectrometry ?
- A flow of charge is produced and the greater the size of the current produced, the greater the abundance of that particular ion.
What happens during the Analysis Stage of Mass Spectrometry?
- A spectra is produced from the current values and the flight time and the spectra will display the relative abundance of each isotope displayed.
Can mass spectroscopy give us an idea of the different isotopes of an atom?
Yes
What is a molecular ion?
The positive ion formed in mass spectrometry when a molecule loses an electron
What is fragmentation?
The process in mass spectrometry that causes a positive ion to split into pieces, one of which is a positive fragment ion
Why do the isotopes of an elememt react in the same way?
Because they all have the same electronic configuration
What does the abundance tell us?
How common each isotope os
What does each positive ion gain from the detector?
Electrons e.g ions with a single positive charge will gain a single electron
What is used to determine the abundance of each isotope?
The size of the current produced when each isotope hits the detector
Will a more abundant isotope produce a lesser or greater current?
A greater current
What is the interior of the mass spectrometer?
A vacuum to prevent the molecules from colliding with molecules in the air
What does m/z represent?
Mass to charge ratio
What are the 2 isotopes of chlorine?
Chlorine 37 and chlorine 35
Why can mass spectrometry be carried out to a high level of precision?
Becasue the mass spectre can be detected to 5 decimal places
What is it called when mass spectrometry is carried out to one decimal place?
The process is called low resolution mass spec
After ionisation, what are we left with?
A molecule that has a positive charge and a radical
Does mass spectra only produce peaks at the positive charges, not the radicals?
Yes, only at the positive charges
Which part of the mass spectrometer separates ions of different masses?
The magnetic field
What is an isotope?
An element with the same number of protons, but a different number of neutrons
Id the ion detected by the mass spectrometer had lost 2 electrons instead of one, what would the size of the peak be like?
The size of the peak would be halved
What causes a molecular ion peak to not be formed in the mass spectrum?
The molecular ion being unstabl e
How does burning with a smoky flame affect the value of the experimentally determined enthalpy change of combustion?
- As this is incomplete combustion, the value will be less exothermic than the data book value.
