Finals week? or my final week...
What is electrochemistry?
the branch of analytical
chemistry that uses electrical measurements of
chemical systems for analytical purposes
What is electric current?
quantity of charge flowing
each second through a circuit.
units of current are amps (A)
what is a flow cell?
like a fuel cell except the products
are separately stored and converted to reactants
upon recharge.
Examples of flow cells include high-capacity lithium-
ion batteries found in laptops, cell phones, and
tablets.
what is spectrophotometry?
in a broad sense, is defined
as any method using light to measure chemical
concentrations
what is beers law?
relates
absorbance, concentration and path length.
A = abc A = εbc
c is the
concentration in
mass units
a is called the
absorptivity or
extinction
coefficient
c is the
concentration in
mol/L
ε is called the molar
absorptivity or
molar extinction
coefficient
What equation is electric charge measured by?
q = (n)(N)(F)
q is the total electric charge in Coulombs. A single
electron or proton has a charge of 1.602 x 10-19 C.
n is the unit charge on a molecule or ion (i.e. Al3+
= 3, Ca+2 = 2, K+ = 1, Cl- = 1
N is the number of moles
F is Faraday’s constant (9.649 x 104 C/mol)
What is the potential difference
denoted as E, between two points is the
work required to move a like charge or work that can
be done when an opposite charge moves between
those points.
measured in volts
what is an indicator working electrode?
an electrode
that responds to the analyte activity
the electrical conductor (the Pt wire) that exchanges
electrons with the indicator half-cell.
what is irradiance?
is the energy per second per unit
area of the light beam.
what part of a molecule is responsible for light
absorption
chromophore
what is ohm's law?
states that current, I (amperes), is directly
proportional to the potential difference, E (volts),
across a circuit and inversely proportional to the
resistance, R (ohms)
I = E/R
What is work and what is its equation?
when charge, q, moves through potential difference,
E, the work required to move the charge to a higher
energy, or the work done by the charge moving to a
lower energy, is expressed as follows
Work = E x q
what are the three important reference electrodes and reduction potential for potententiometry?
Standard Hydrogen Electrode (S.H.E.)
Pt(s)|H2 (g)|H+ Eo = 0 Volts
Harder to use because of constant H2 (g) and Pt
catalyst is expensive and easily poisoned.
Silver-Silver Chloride Electrode. KCl is saturated.
Ag|AgCl Eo = 0.222 Volts
Esat’d KCl = 0.197 Volts
Saturated Calomel Electrode (S.C.E.). Calomel is
Hg2Cl2. KCl is saturated
Hg22+|Hg Eo = 0.268 Volts
Esat’d KCl = 0.241 Volts
what is the monochromator?
light filter) is used to select
one wavelength of light. Light that is very narrow in
range is said to be monochromatic (one color).
what are spectrophotometric tritrations?
the changes in
absorbance during a titration are monitored to
determine the equivalence point.
what is power?
Power is the work done or required per unit of time.
The SI unit of power is J/s, or watts (W).
Since q/s is the current, I
P = E x I
what are galvanic cells?
also called a voltaic cell) use spontaneous redox
reaction to generate electricity
oxidation occurs at the anode and reduction occurs at the cathode
What is the nerst equation?
Ecell
o = Ecathode
o - Eanode
o
Reduction occurs at the Cathode
Oxidation occurs at the Anode
Ecell = Ecell
o - RT
nF (lnQ)
In potentiometry R (gas law constant), T (room
temperature, 25 oC = 298 K), and F are constant.
n potentiometry this equation simplifies:
Ecell = Ecello + (0.05916/n ) (log [Reduced])
what is transmittance?
defined as the fraction of the
original light that passes through the sample.
Therefore, T has the range 0 to 1. The percent
transmittance ranges between 0 and 100%.
what is self absorption?
what is the retention time?
what is retention volume?
what is separation factor?
what is k?
Then emission decreases (quenched)
because of self-absorption.
Quenching by self-absorption occurs when the
analyte absorbs its own excitation or emission
irradiance.
R, for each component is the
time that elapses between the injection and the
arrival of that component at the detector.
VR, is the volume of mobile
phase required to elute a particular solute from
the column.
is the ratio
of their adjusted retention times.
retention factor, the adjusted
retention time expressed in multiples of the tM
what is a fuel cell?
uses fresh reactants that flow past the
electrodes, with products flushed from the cell
what is a reference electrode?
half-cell with a fixed
composition, so it has a constant potential. The RE
is the half-cell on the left and the salt bridge
what is junction potential
voltage difference present
at the interface between two dissimilar electrolyte
solutions. This limits the accuracy of potentiometric
measurements
what is absorbance?
because it is directly
proportional to the concentration of the light-
absorbing species in the sample.
what is chromatography?
what is the mobile phase?
what is the stationary phase?
What is eluent and eluate?
Chromatography operates on the same principle
as extraction, but one phase is held in place
while the other moves past it.
solvent moving through the column. Can be a liquid or gas
material that stays
in place inside the column.
The fluid entering the column is called the
eluent and the fluid exiting the column is called
the eluate