Title: Unused Qs

Q: The spectral region 8-14 micron, 700-1250 cm^-1 is a critical window for radiation from earth escaping to space.
Which of the following statements best describes the gas CBr_4 ?

(Hint: IR spectra may be found on the NIST chemistry webbook.)
- Not a greenhouse gas, as it does not absorb IR radiation at all
- Absorbs IR radiation, but not in the greenhouse window region
- Has a strong IR absorption band in the greenhouse window region
- Can’t be a greenhouse gas because there’s no such thing (Yeah, and smoking doesn't cause cancer either.)
A: Absorbs IR radiation, but not in the greenhouse window region

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: 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: 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 {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.

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: 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: 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: The spectral region 8-14 micron, 700-1250 cm^-1 is a critical window for radiation from earth escaping to space.
Which of the following statements best describes the gas CS_2?

(Hint: IR spectra may be found on the NIST chemistry webbook.)
- Not a greenhouse gas, as it does not absorb IR radiation at all
- Absorbs IR radiation, but not much in the greenhouse window region
- Has a strong IR absorption band in the greenhouse window region
- Can’t be a greenhouse gas because there’s no such thing (Yeah, and smoking doesn't cause cancer either.)
A: Absorbs IR radiation, but not much in the greenhouse window region