# Q1: Molar absorbtivity is the measure of the

A amount of light absorbed per unit length
B amount of light absorbed per unit concentration
C amount of light reflected and absorbed per unit concentration
D None of the above

ANS:B - amount of light absorbed per unit concentration

Molar absorptivity =A/CL.

Molar absorptivity is depended upon path length, then why the answer is B?

# Q2: Vibrational spectroscopy is

A a large mass on a weak spring
B a flashlight through a prism and shake it
C a class of spectroscopic techniques which analyzes molecular motions
D an Infrared spectroscopy

ANS:C - a class of spectroscopic techniques which analyzes molecular motions

# Q3: Which of the following will oscillate the fastest?

A A large mass on a weak spring
B A large mass on a stiff spring
C A small mass on a stiff spring
D A small mass on a weak spring

ANS:C - A small mass on a stiff spring

# Q4: Molar absorbtivities of compounds exhibiting charge transfer absorption are

A small
B moderate
C large
D none of these

ANS:C - large

Species that exhibit charge-transfer absorption are of particular importance because their molar absorptivities are very large (max > 10,000). Thus, these complexes provide a highly sensitive means for detecting and determining absorbing species. Complexes exhibit charge transfer absorption are called charge-transfer complexes. In order for a complex to exhibit a charge-transfer spectrum, it is necessary for one of its components to have electron-donor characteristics and for the other component to have electron-acceptor properties. Absorption of radiation then involves the transfer of an electron from the donor to an orbital that is largely associated with the acceptor.

# Q5: In the equation, A = ε bc, what quantity is represented by "ε"?

A Absorbtivity
B Molar absorbtivity
C Path length
D None of these

ANS:B - Molar absorbtivity

A is Absorbance or optical density or extinction coefficient.
C is concentration.
T pathlength.

# Q6: Beer's Law states that

A absorbance is proportional to both the path length and concentration of the absorbing species
B absorbance is proportional to the log of the concentration of the absorbing species
C absorbance is equal to P0 / P
D none of the above

ANS:A - absorbance is proportional to both the path length and concentration of the absorbing species

Beer's law resulted to the concentration of absorbing species.

Lambert's law related to thickness/pathlength of absorbing species.

# Q7: Why must the voltage supplied to a tungsten lamp be very stable?

A Because if it wasn't, the lamp would bum out
B Because amount of energy the lamp emits is proportional to the fourth power of the operating voltage
C Because the lamp will only function at a specific voltage
D All of the above

ANS:B - Because amount of energy the lamp emits is proportional to the fourth power of the operating voltage

# Q8: A simple harmonic oscillator may absorb energy

A at anytime.
B when the frequencies match exactly
C when the amplitudes are the same.
D at no time.

ANS:B - when the frequencies match exactly

When there is a match of frequency, energy is been absorb.

# Q9: Where does a carbonyl (C=0) stretch appear in an IR spectrum?

A 1740-1720
B 1870-1650
C 3640-3250
D 160-110

ANS:B - 1870-1650

# Q10: Why is it generally preferable to use absorbance as a measure of absorption rather than % transmittance?

A Because %T cannot be measured as accurately as absorbance
B Because %T is dependant on the power of the incident radiation
C Because absorbance is proportional to the concentration of the analyte, whereas %T is not
D none of the above

ANS:C - Because absorbance is proportional to the concentration of the analyte, whereas %T is not

# Q11: Which of the following components of a monochromator is the dispersing element?

A The collimating lens
B The entrance slit
C The diffraction grating
D None of these

ANS:C - The diffraction grating

# Q12: Which of the following relationships between absorbance and %transmittance is incorrect?

A A = log10 100 / %T
B A = 2 - log10 %T
C A = log10 1 / T
D All are correct

ANS:C - A = log10 1 / T

I think the correct answer is D]. All are correct.

A Stretching
B Scissoring
C Rocking
D Rolling

ANS:D - Rolling

# Q14: Why are rotational transitions of little use to a spectroscopist?

A Because the energy required to induce a rotational transition is so small that it cannot be measured
B Because rotational transitions are extremely rare
C Because, in liquids and solids, spectral lines corresponding to rotational transitions are broadened as the result of molecular collisions and other interactions
D All of the above

ANS:C - Because, in liquids and solids, spectral lines corresponding to rotational transitions are broadened as the result of molecular collisions and other interactions

# Q15: In the past, IR spectra had to be aquired one wavelength at a time, which took a long time. Today quick spectra is due to the

A the Fourier Transfer Algorithm allows us to scan all frequencies at once
B light is faster today that it used to be
C absence of broad spectrum of wavelenth
D none of the above

ANS:A - the Fourier Transfer Algorithm allows us to scan all frequencies at once

# Q16: UV-Vis spectroscopy of organic compounds is usually concerned with which electronic transition(s)?

A σ → σ*
B n → σ*
C n → π* and π → π*
D none of these

ANS:C - n → π* and π → π*

Non bonded electrons to Ïƒ* transitions are considered too? Explain, please.

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