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Flashcards in Relative Mass Deck (7)
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Significance of carbon 12

Mass of carbon 12 isotope defined as exactly 12 atomic mass units
Standard mass for atomic mass is the mass of 1/12 of carbon 12 atom


Relative isotopic mass

Mass of an isotopic relative to 1/12th of the mass of a carbon 12 atom


Relative atomic mass

Weighed mean mass of an atom of element relative to 1/12th mass of carbon 12
Takes into account, percentage abundance of each isotope, relative isotopic mass of each isotope


Determination of relative atomic mass

Mass spectrometer gives % abundance
Sample vaporised, ionised to form cations
Ions accelerated, heavy ions move more slowly, harder to deflect than lighter ions
Ions detected on mass spectrum as mass/charge ratio


How to calculate % abundance?

Peak height/ total height of all peaks x 100


How to calculate RAM?

Mass x %


Determination of relative isotopic mass

Mass spectrometer can record accurate m/z ratio for each isotope so accurate values of RIM can be measured