Molecular Mass. Mass of Atom Measured in atomic mass unit (amu) 1 amu = 1.66 x 10 -24 g Defined by assigning the mass of 12 amu to the carbon-12 isotope.

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Presentation transcript:

Molecular Mass

Mass of Atom Measured in atomic mass unit (amu) 1 amu = 1.66 x g Defined by assigning the mass of 12 amu to the carbon-12 isotope

Average Atomic Mass This is what is shown on periodic table Average of all naturally occurring isotopes Can determine by using the masses of the various isotopes and their relative abundances Average atomic mass is also called atomic weight

Example Carbon consists of three isotopes. The 1 st has a mass of 12 amu and makes up %. The 2 nd, amu and is 1.108%. The 3 rd is amu and is 1 x %. What is the average atomic mass?

Molar Mass The generic term for the mass of one mole. The same as gram molecular mass, gram formula mass, and gram atomic mass.

Examples Calculate the molar mass of the following and tell me what type it is. Na 2 S N 2 O 4 C Ca(NO 3 ) 2 C 6 H 12 O 6 (NH 4 ) 3 PO 4

Percent Composition Percentage of each element in a compound by mass Calculate the percentage of each element in sucrose (C 6 H 12 O 6 ).

Mass Spectrometer Instrument used for determining weights of elements or compounds Gas sample is bombarded with high energy electrons Collisions between molecules and electrons produce + ions Ions are focused into a beam by passing between two slits

Beam then passes between the poles of a magnet which curves the path of the beam Ones with greater mass curve more

Separation By changing the strength of the magnetic field, you can adjust for different mass ions to reach the detector At the detector a graph of intensity signal is produced