Title: CHE2FND_Spectroscopy_Quiz

Remember to complete the OWL Q’s also! Follow the link on LMS, and do both IR spectroscopy OWL assignments - required (a) and required (b).

Q: A lamp emits light of wavelength {w} nm.
What is the energy of this radiation in kJ mol^-1?
A: round(119626/{w},0) (formula; values not in the backup's text)
Feedback: Be sure to use S.I. units - ie express wavelength in m. Also, E(kJ mol^-1) = E(J).N_A/1000

Q: A {watt} W microwave oven emits radiation at 2.45 GHz.
How many photons are emitted each second?
--
Hint (a) Watts, W = Joules per second.
Hint (b) Large numbers may be entered using exponential notation,
.            for example, 251 million may be written as 2.51E+8
A: {watt}*6.16E23 (formula; values not in the backup's text)
Feedback: Calc energy per photon using E = h ν. Remember GHz = 10^9 Hz.

Q: For a photon of {wn} cm^-1, what is the corresponding frequency in GHz?
A: round(29.979*{wn},0) (formula; values not in the backup's text)
Feedback: Remember to convert cm-1 into S.I. units, and that GHz is 10^9 Hz.

Q: IR spectra may be displayed using wavelength or wavenumber. What is the
corresponding wavenumber value (cm^-1) for a peak at wavelength {lambda} μm?
(1 μm = 10^-6 m)
A: round(10000/{lambda},0) (formula; values not in the backup's text)
Feedback: Wavenumber is the reciprocal of wavelength. Use compatable units - ie express wavelength in cm.

Q: If a sample absorbs {pa}% of the light at a given wavelength,
what is the corresponding absorbance value.
- {=-log10(1-{pa}/100)}
- {={pa}/100}
- {=1-{pa}/100}
- {=-log(1-{pa}/100)} (Use base 10 log, not natural log to calculate absorbance)
- {=1+log10(1-{pa}/100)}
- {={pa}}
A: {=-log10(1-{pa}/100)} (formula; values not in the backup's text)
Feedback: Absorbance is not = % of light absorbed, it is a logarithmic quantity. First calculate transmittance, then absorbance.

Q: what's the product of {y1} and {y2}?
- ={y1}+{y2}
- ={y1}*{y2}
- It must be {={y1}*{y2}} elephants
A: ={y1}*{y2} (formula; values not in the backup's text)

Q: IR spectra may be displayed using wavelength or wavenumber.
What is the corresponding wavenumber value (cm^-1) for a peak at wavelength {lambda} μm?
(1 μm = 10^-6 m)
- {=10000/{lambda}}
- {=1/{lambda}}
- {=1000000/{lambda}}
- {=100*{lambda}}
- {=30*{lambda}}
- {=299792458/{lambda}}
- {=299792458*1e6/{lambda}}
- {=2.99792458e3/{lambda}}
A: {=10000/{lambda}} (formula; values not in the backup's text)
Feedback: Wavenumber is the reciprocal of wavelength. Use compatible units - ie express wavelength in cm.

Q: If a sample absorbs {pa}% of the light at a given wavelength,
what is the corresponding absorbance value?
- {=-log10(1-{pa}/100)}
- {={pa}/100}
- {=1-{pa}/100}
- {=-log(1-{pa}/100)} (Be sure to use log 10, not natural log to calc absorbance.)
- {pa}
- {=1+log10(1-{pa}/100)}
A: {=-log10(1-{pa}/100)} (formula; values not in the backup's text)
Feedback: Absorbance is not = % of light absorbed, it is a logarithmic quantity. First calculate transmittance, then absorbance.

Q: For a photon of {wn} cm^-1, what is the corresponding frequency in GHz?
- {=29.979*{wn}}
- {=29.979*1e9*{wn}}
- {=100/{wn}}
- {={wn}/29.979}
- {={wn}/29.979/1e9}
- {=299792458}
- {=1e7/{wn}}
- {=1e3/{wn}}
- {=29.979*1e7*{wn}}
A: {=29.979*{wn}} (formula; values not in the backup's text)
Feedback: Remember to convert cm-1 into S.I. units, and that GHz is 10^9 Hz.

Q: A lamp emits light of wavelength {w} nm.
What is the energy of this radiation in kJ mol^-1?
- {=119626/{w}}
- {=119626000/{w}} (convert from J mol-1 to kJ mol-1)
- {=1.98645e-19/{w}} (compute per mol, not per molecule)
- {=1.98645e-16/{w}}
- {=19864.5/{w}}
- {=198645/{w}}
- {=1e6/{w}}
A: {=119626/{w}} (formula; values not in the backup's text)
Feedback: Be sure to use S.I. units - ie express wavelength in m. Also, E(kJ mol^-1) = E(J).N_A/1000

Remember to register for OWL, and login to complete the other part of this assignment, where required OWL questions for credit found in the folder labelled “spec assignment”.
The link and instructions are found on LMS.

Q: The fundamental vibrational transition of a diatomic molecule is observed at {wn} cm^-1. What is the population of the 1st excited vibrational energy level, expressed relative to the population of the ground vibrational state, i.e. N_1/N_0, at {t} degrees Celsius? Quote your answer to 3 decimal places.
A: round(exp(-{wn}/(0.69504*({t}+273.15))),3) (formula; values not in the backup's text)
Feedback: Applying Boltzmann equation, be sure to use consistent units for numerator and denominator, and also convert temperature to Kelvin.

Q: This and the following questions require some knowledge of IR band positions for various functional groups. For more info, refer to:
* McMurray textbook, chapter 12

* IR bands tabulated by functional group
* IR bands sorted by wavenumber

And now for the question: Which best describes a carbonyl stretch band?
- 2100 cm^-1, sharp, weak intensity
- 1700 cm^-1, sharp, strong intensity
- 1600 cm^-1, sharp, medium intensity
- 3500 cm^-1, broad, strong intensity
A: 1700 cm^-1, sharp, strong intensity

Q: If a sample absorbs {pc}% of the light at a given wavelength,
what is the corresponding absorbance value to 2 decimal places?
A: round(-log10(1-{pc}/100),2) (formula; values not in the backup's text)
Feedback: Absorbance is not = % of light absorbed, it is a logarithmic quantity. First calculate transmittance, then absorbance.

Q: If a sample absorbs {pc}% of the light at a given wavelength,
what is the corresponding absorbance value to 2 decimal places?
A: round(-log(1-{pc}/100),2) (formula; values not in the backup's text)
Feedback: Absorbance is not = % of light absorbed, it is a logarithmic quantity. First calculate transmittance, then absorbance.