ANALYTICAL CHEMISTRY FINAL- ACS EXAM QUESTIONS
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Wavelength
the distance in a period of waves: nm or m (c=vlambda)
Frequency
the number of complete oscillations in a second: Hz
Plank's constant
6.626 10 -34 J Hz-1
Transmittance
T=P/Po
Absorbance
A=log(Po/P)=-logT
Beer's law
A=ebc
Absorbance accumulation if mixtures
Atotal= A1+A2+...+An=e1b1c1+e2b2c2+...enbncn
Excited singlet
n > π and π.n
Excited triplet
n> π*
Excitation spectrum
measured by varying the excitation wavelength and measuring emitted light at one
particular wavelength
Emission spectrum
a graph of emission intensity v. emission wavelength
Emission intensity at low concentration
I=kP0c
Electrolysis
process in which a direct electric current (DC) is used to drive a non-spontaneous
chemical reaction to occur at an electrode by an imposed voltage
Working electrode
electrode at which the reaction of interest occurs
Counter electrode
assists working electrode
Where does electrolysis occur?
On both electrodes
Ohmic potential
voltage needed to overcome electrical resistance (R)
Eohmic
IR
coulomb (q)
It (amperes seconds)
Moles of e-
, coulombs/(coulombs/mole)=(I*t)/F
Moles reacted
I*t/nF
battery voltage
Ebattery
Overpotential
Eover
Cell potential
Ecell=Ecathode-Eanode
Voltage relation around the circuit
Ebattery=Ecell-Eover-Eohmic
Over potential
the voltage required to overcome the activation energy for the reaction to occur at the
electrode surface
Relation to gas-production and overpotential
Gas-producing reaction requires higher activation energy, thus higher overpotential is
needed
Relation between overpotential and current density
Greater overpotential sustains a higher current density
What does a faster reaction require?
Greater overpotential
Activation energy depends on what?
The nature of the surface
What are the three electrodes in a 3-electrode cell?
Working, auxiliary, and reference
Working electrode
where the analytical reaction occurs
Auxillary electrode
the other electrode needed for the current flow
Reference electrode
used to measure the potential of the working electrode
Which 2 electrodes does current flow between?
WE and AE
What is unaffected on the RE?
ohmic potential, concentration polarization, and overpotential
What instrument measures the controlled-potential electrolysis?
potentiostat
Where is the placement of the electrodes compared to a potentiostat?
Potentiostat used between WE and RE and the RE should be close as possible
Why should the Re be placed as close as possible to a potentiostat?
to obtain the best measurement of WE potential
What is quantitatively deposited on an electrode by electrolysis?
Analyte
-0.911 to -2 V
reduction of Cu2+
Residual current
AND ANSWERS A+ GRADED. BUY Quality Materials!
Wavelength
the distance in a period of waves: nm or m (c=vlambda)
Frequency
the number of complete oscillations in a second: Hz
Plank's constant
6.626 10 -34 J Hz-1
Transmittance
T=P/Po
Absorbance
A=log(Po/P)=-logT
Beer's law
A=ebc
Absorbance accumulation if mixtures
Atotal= A1+A2+...+An=e1b1c1+e2b2c2+...enbncn
Excited singlet
n > π and π.n
Excited triplet
n> π*
Excitation spectrum
measured by varying the excitation wavelength and measuring emitted light at one
particular wavelength
Emission spectrum
a graph of emission intensity v. emission wavelength
Emission intensity at low concentration
I=kP0c
Electrolysis
process in which a direct electric current (DC) is used to drive a non-spontaneous
chemical reaction to occur at an electrode by an imposed voltage
Working electrode
electrode at which the reaction of interest occurs
Counter electrode
assists working electrode
Where does electrolysis occur?
On both electrodes
Ohmic potential
voltage needed to overcome electrical resistance (R)
Eohmic
IR
coulomb (q)
It (amperes seconds)
Moles of e-
, coulombs/(coulombs/mole)=(I*t)/F
Moles reacted
I*t/nF
battery voltage
Ebattery
Overpotential
Eover
Cell potential
Ecell=Ecathode-Eanode
Voltage relation around the circuit
Ebattery=Ecell-Eover-Eohmic
Over potential
the voltage required to overcome the activation energy for the reaction to occur at the
electrode surface
Relation to gas-production and overpotential
Gas-producing reaction requires higher activation energy, thus higher overpotential is
needed
Relation between overpotential and current density
Greater overpotential sustains a higher current density
What does a faster reaction require?
Greater overpotential
Activation energy depends on what?
The nature of the surface
What are the three electrodes in a 3-electrode cell?
Working, auxiliary, and reference
Working electrode
where the analytical reaction occurs
Auxillary electrode
the other electrode needed for the current flow
Reference electrode
used to measure the potential of the working electrode
Which 2 electrodes does current flow between?
WE and AE
What is unaffected on the RE?
ohmic potential, concentration polarization, and overpotential
What instrument measures the controlled-potential electrolysis?
potentiostat
Where is the placement of the electrodes compared to a potentiostat?
Potentiostat used between WE and RE and the RE should be close as possible
Why should the Re be placed as close as possible to a potentiostat?
to obtain the best measurement of WE potential
What is quantitatively deposited on an electrode by electrolysis?
Analyte
-0.911 to -2 V
reduction of Cu2+
Residual current
