Relative mass
- Created by: Rosyposyxx
- Created on: 02-07-17 17:01
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- Relative mass
- The mass of a carbon-12 isotope is defined as exactly 12 atomic mass units, 12u
- 1u= 1/12th the mass of a carbon 12 atom
- Approx the mass of a proton or neutron
- 1u= 1/12th the mass of a carbon 12 atom
- Relative isotopic mass is the mass of an isotope relative to 1/12th of the mass of an atom of carbon-12
- Most elements contain a mixture of isotopes, each with a different isotopic mass
- Relative atomic mass, Ar, is the weighted mean mass of an atom of an element relative to 1/12th of an atom of carbon-12
- Weighted mean mass takes account of- percentage abundance of each isotope and relative isotopic mass of each isotope
- Found using a mass spectrometer
- A sample is vaporised and ionised to form positive ions, the ions are accelerated and heavier ions move slower and are harder to deflect so they separate. Ions are detected as m/z
- m/z= mass to charge ration= relative mass of ion divided by relative charge of ion
- A sample is vaporised and ionised to form positive ions, the ions are accelerated and heavier ions move slower and are harder to deflect so they separate. Ions are detected as m/z
- Found using a mass spectrometer
- To find Ar of an isotope. Ar= (%iso1xMassnoiso1)+(%iso2xMassnoiso2) divided by 100 or total abundance
- Weighted mean mass takes account of- percentage abundance of each isotope and relative isotopic mass of each isotope
- The mass of a carbon-12 isotope is defined as exactly 12 atomic mass units, 12u
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