Chemistry 254 Exam 2
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| White Noise | random noise, also called Gaussian noise, due to random movement of charge carriers in an electric circuit or from random arrival of photons or charge carriers to a detector
=/=F(v)
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| 1/F Noise | biffer at low frequencies, associated with slow drift
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| Line Noise | specific to various frequencies
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| Signal | response given by instrument
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| Signal-to-Noise Ratio (S/N) | the height of the signal divided by the noise in the baseline around the signal. The higher the signal-to-noise ratio, the less uncertainty there is in the signal
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| Smoothing | use of mathematical procedure or electrical filtering to improve the quality of the signal
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| Polynomial Least Squares Fit | fits to moving groups of >=7 points and then pieces them together
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| Atomization | process in which a compound is decomposed into its atoms at high temperatures
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| Nebulizer | breaks the liquid sample into a mist of fine droplets
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| Premix Burner | a burner in which the sample is nebulized and simultaneously mixed with fuel and oxidant before being fed into the flame
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| Plasma | a gas that is hot enough to contain free ions and electrons, as well as neutral molecules
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| Graphite Furnace | a graphite tube that can be heated electronically to about 2500K to decompose and atomize a sample for atomic spectroscopy
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| Chemical Interference | any chemical reaction preventing free atoms like fermentation of stable oxides and formation of non volatile salts
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| Ionization Interference | when atoms you want to observe form ions that have different absorption/emission lambdas
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| Spectral Interference | the overlap of analyte signal with signals due to other elements or molecules in the sample
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| Releasing Agent | a chemical added to a sample to decrease chemical interference
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| Ionization Suppressor | decreases the extent of ionization of analyte
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| Heisenberg Uncertainty Principle | the shorter the lifetime of the excited state, the more uncertain is its energy
(delta)E * (delta)t >= n/4(pi)
OR
((delta)E)/E = ((delta)(lambda))/(lambda)
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| Linewidth | used interchangeably with bandwidth
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| Pressure Broadening | line broadening due to collisions between molecules
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| Hollow Cathode Lamp | a lamp that emits sharp atomic lines characteristic of the element from which the cathode is made
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| Continuum Source Background Correction | Hollow Cathode Lamp: A = Aana. + A(background)
W Lamp: A ~= A(background)
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| Zeeman Effect | splitting degenerate E levels in B(vector) field, this exploits polarization of different transitions
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| Boltzmann Distribution | relative population of two states at thermal equilibrium
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| Inductively Coupled Plasma | a high temperature plasma that derives its energy from an oscillating radio-frequency field
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| Mass Spectrum | a graph showing the relative abundance of each ion as a function of its mass-to-charge ratio
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| Base Peak | most intense peak in a mass spectrum
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| Molecular Ion | an ion that has not lost or gained any atoms during ionization
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| Ion Focusing Lens | has a small potential that creates a focused beam
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| Acceleration Plate | has high voltage between plates that imparts a high velocity to ions as they are expelled from the bottom of the ion source
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| Resolving Power | m/(delta)m where "(delta)m" is the separation of two peaks when the overlap at the base is 10% of the peak height and m is the smaller of the two m/z values
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| Electron Impact Ionization | interaction of analyte molecules (M) with high energy electrons in the ion source of a mass spectrometer to give the cation radical, M^t0, and fragments derived from M^t0
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| Chemical Ionization | a gentle method of producing ions for a mass spectrometer without extensive fragmentation of the analyte molecule (M). A reagent gas such as CH4 is bombarded with electrons to make CH5+, which transfers H+ to M, giving MH+
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| Magnetic Sector Mass Spectrometer | a device that separates gaseous ions that have the same kinetic energy by passing them through a magnetic field perpendicular to their velocity. Trajectories of ions with a certain mass-to-charge ratio are bent exactly enough to reach the detector
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| Double Focusing Mass Spectrometer | a spectrometer that uses electric and magnetic sectors in series to obtain high resolution
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| Transmission Quadruple Mass Spectrometer | separates ions by passing them between four metallic cylinders to which are applied direct current and oscillating electric fields. Resonant ions with the right mass-to-charge ratio pass through the chamber to the detector while nonresonant ions are lost
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| Time of Flight Spectrometer | ions of different mass accelerated through the same electric field have different velocities. The lighter ions move faster. The time-of-flight spectrometer finds the mass-to-charge ratio by measuring the time that each group of ions requires to tavel
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| Reflection | converts apparent big O(Ek) into apparent small O(FK)
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Created by:
Marlene the Chemist
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