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CH4171-CH11 mass spectrometry with concept tests

# CH4171-CH11 mass spectrometry with concept tests -...

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Chemistry in Context Life on Mars. The Viking and Phoenix landers were sent to Mars to determine if life ever existed there. What were these spacecrafts looking for and how did they perform the analyses?

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Mass Spectrometry Concept Te\$t The 12.01 on the periodic table for C indicates that: (A) A carbon atom weighs 12.01 g (B) A carbon atom weighs 12.01 lbs (C) A carbon atom weighs 12.01 x 10 -24 g (D) It does not indicate anything pertaining to the absolute mass of a carbon atom
Mass Spectrometry What is atomic mass? Atomic mass units (amu) or daltons (Da): Defined relative to 12 C, which is assigned a mass of exactly 12 amu. H has a mass of 1.008 relative to carbon-12, so it is assigned a mass of 1.008 amu. 1 amu = 1 Da = an absolute mass of 1.6605387 x 10 -27 kg The mole provides the link between numbers of atoms and mass of atoms. It is defined as the amount of a substance that contains the same number of entities as there are atoms in exactly 12 g of C-12. This number is Avogadro’s number. Example: 1.008 amu/6.02 x 10 23 = 1.67 x 10 -24 g

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Mass Spectrometry Mass to charge ratio A unitless ratio of mass number to the number of charges, z, on the ion. For 12 C 1 H 4 + (methane cation) the m/z is 16.0313/1. For 13 C 1 H 4 2+ the m/z is 17.0346/2 = 8.5173. Ions in mass spec are usually singly charged so the z is frequently dropped, but this is not strictly correct. A mass spectrometer is an instrument that produces ions and separates them according to their mass-to-charge ratios, m/z.
Mass Spectrometry General steps (1) Atomization (2) Ionization (3) Separation of ions (4) Detection-Counting the ions General Schematic 10 -5 – 10 -8 Torr Inlet Mass Analyzer

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Molecular Mass Spectra M : ionize M + . fragment m 1 + + m 2 …. Where M is a molecule and m x are fragments of M M + is called the molecular ion M : + e - M + + 2e - . This is often done via electron bombardment:
Molecular Mass Spectra Ion-molecule collisions often occur: ABCD .+ + ABCD (ABCD) 2 .+ BCD . + ABCDA + Collision Fragmentation Typically only hydrogen atom transfer is observed, which yields a peak at m/z = (M+1) +

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Mass Spectra Molecular Ion: Unfragmented molecule that has lost an electron Base Peak: Highest intensity peak, assigned an intensity of 100%. Fragment Ions: Stable carbocations of the parent molecule. *Key Concepts
Mass Spectra Notice the successive loss of m/z = 14. This corresponds to fragments of the molecular ion that have lost CH 2 .

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Mass Spectra
Concept Test The spectrum below is from a hydrocarbon containing which substituent? (A) Cl (B) –C 5 H 5 (C) Br (D) OH CH 3 CH 2 CH 2 Br

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Teams of the Week Team Accomplishing Chemistry Objectives (TACO) Amy Marks, Robin Newcome, Jacob Howard WoW Children’s Museum Provides educational, interactive exhibits and programs for all children. Jacob volunteers for them. FeMaiden Mark Cheuvront, Cody Danko, and Francis Dragotta I have a dream foundation Motivates and empowers children from low-income families to reach their education and career goals.
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CH4171-CH11 mass spectrometry with concept tests -...

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