CHE 113- Midterm Exam Guide - Comprehensive Notes for the exam ( 49 pages long!)

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Published on 13 Oct 2017
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Syracuse
CHE 113
MIDTERM EXAM
STUDY GUIDE
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Chapter 12
Antoine Lavoisier
oLaw of conservation of mass
Atoms are neither created nor destroyed in chemical reactions
Forensic chemical analysis
oTypical chemical problems
What is the compound?
Were two substances one unit in the past?
Did a fiber come from the victim or another source?
oCombustion analysis
oMass spectrometry
oAtomic spectroscopy
Atomic absorption and emission analysis
Neutron activation analysis
oMolecular spectroscopy
Electronic
Vibrational
Nuclear magnetic resonance
ox-ray methods
x-ray diffraction
Energy dispersive x-ray fluorescence
Analytical methods
oQuestions to consider in choosing an analytical method
Quantitative or qualitative
Sample size and sample preparation requirements
What level of analysis is required
Detection levels and useful analytical concentration ranges
Destructive or non-destructive
Availability of instrumentation
Admissibility (are all compositionally the same or are there sufficient
variations among known objects to link two samples)
Atomic theory - isotopes
oDifferences/similarities between atoms of an element
All atoms of a given element have the same number of protons and
same number of electrons
Atoms of an element may have different numbers of neutrons
Called isotopes
Combustion reactions
oReaction of hydrogen with oxygen
oOrganic compounds
C to CO2 and H to H2O
oUse CO2 and H2O to determine the amount of C and H in original sample
oTells how much of each element is present in unknown sample
oAllows determination of % of each element in the sample
Mass spectrometry
oCreates charged particles (ions) from gas phase molecules
Electron ionization (EI)
Uses electron impact to ionize a molecule
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Chemical ionization (CI)
First ionizes a molecular gas which in turn ionized the molecule
of interest; a gentler method of ionization
Fast atom bombardment (FABS)
Mainly for involatile compounds; very harsh
oThe MS analyzes ions to provide information about the molecular weight of the
compound and its chemical structure
oIonization produces singly charged ions; the intact charged molecule is the
molecular ion; energy from the electron impact and instability in a molecular ion can
cause that ion to break into smaller pieces
Chromatography
oUsed to separate mixtures of compounds
oBased upon the differing interactions between the components of a mixture and
some other compound
oChromatographic systems have a stationary phase (which can be solid or liquid)
and a mobile phase (usually liquid or gas)
oMixture to be separated is placed at the beginning of the chromatographic
system (stationary phase)
oThe mobile phase then pushes the components of the mixture through the
system
oEach components absorbs on the stationary phase with a different strength
(stronger means moves more slowly through the system)
oEach component comes out the end of the system at a different time
GC-Mass spectrometry
oA mixture is injected into the GC where the mixture is vaporized; the gas
mixture travels through a GC column, where the compounds become separated; those
separated compounds then immediately enter the mass spectrometer
oCases for the GC-MS
Toxicology
Components in blood
Alcohol intoxication
Gunshot residues
Bohr's model
oElectrons in around nucleus with quantized (allowed) energy states
oWhen in a state, no energy is radiated but when it changes states, energy is
emitted or gained equal to the energy difference between the states
oEmission from higher to lower, absorption from lower to higher
Microscopic properties
oLight energy may behave as waves or as small particles (photons)
oParticles may also behave as waves or as small particles
oBoth matter and energy occur only in discrete/allowed units (quantized)
Energy and matter are quantized
Non-quantized
Can be at any position/unit
Spectroscopy
oWhen electromagnetic radiation passes through a substance, it can either be
absorbed or transmitted depending upon the structure of the substance
Vibrational spectroscopy
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