CHEM 121 Lecture Notes - Lecture 4: Chemical Formula, Caffeine, Atomic Mass
19 Jun 2015
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Can separate ions by mass to charge ratio. 2 isotopes, so 3 lines on mass spec (abr - abr, abr - bbr, bbr - bbr) Divide values on mass spec by 2 for outer two line -> a=81, b=79. Mass specs used in etd (explosives trace detectors) used in security devices. Blows off potentially dangerous substances on clothes and detects excessive amounts of dangerous substances. Lon capa example: cocl2 (*good exam question*) Could have 13c16oxclxcl, 13c16oyclycl, 13c16oxclycl, 12c16oxclxcl, 12c16oyclycl, Only 3 lines on graph, so look at abundance of molecules and match to graph (note: 12c much more abundant (98. 89%) than 13c (1. 1%)) Atomic masses on periodic table are average mass in amu. Determined by through relative abundance of isotopes. Atomic mass of c gives as 12. 011 amu. Note: no carbon atoms weigh 12. 011 amu. For elements with only one isotope, value given is exact mass. Unit for counting atoms, can relate number of atoms to mass ample.
