1. Look up the temperatures of the known phase transitions for trans-stilbene, a
ID: 575781 • Letter: 1
Question
1. Look up the temperatures of the known phase transitions for trans-stilbene, ammonium chloride, and p-azoxyanisole that fall in the temperature range 0-200 celsius.
2. The samples are contained in aluminum pans with crimped-on covers. The instrument is stationary during operation, so samples placed in open pans would not spill. Why do you think the covers are needed?
3. What is the refractive index of liquid ethanol at room temperature at wavelengths near 600 nm?
4. What are the fundamental vibrational frequencies of dichloromethane? Which of these vibrations are observed in the infrared spectrum? Which are observed in the Raman spectrum?
5. What is the enthalpy of vaporization, in kJ/mole, of n-hexane at its normal boiling point?
6. What is the activation energy for the cis to trans isomerization of 2-butene in the gas phase?
7. What are the wavelength and peak molar absorptivity of the longest-wavelength maximum in the UV-visible absorption spectrum of –carotene in liquid solution at room temperature?
Explanation / Answer
1. Phase transtition tempwrature of
Trans-stilbene is 124.4 Degree Celcius. (397.40 K)
Ammonium chloride 120 Degree Celcius (465 K)
p-azoxyanisole is 118 Degree Celcius (391 K)
2. Covers are needed so that the samples don't go dry with excessive heat if passed on them directly.
3. Refractive index of liquid ethanol at room temperature at wavelengths near 600 nm is 1.361
4.
313 cm-1
(IR intensity = 0.0086)
(Raman active)
5. The molar enthalpy of vaporization of hexane (C6H14) is 28.9 kJ/mol, and its normal boiling point is 68.73°C.
6. The activation energy for the cis to trans isomerization of 2-butene in the gas phase is 75.3 kJ/mol
7. Beta-carotene absorbs throughout the ultra-violet region into the violet - but particularly strongly in the visible region between about 400 and 500 nm with a peak about 470 nm with peak molar absorptivity of 1.4 * 105
C-H symmetric stretching(a1) C-H asymmetric stretching
(b1) H-C-H in-plane scissoring
(a1) 3077 cm-1
(IR intensity = 0.065)
(Raman active) 3037 cm-1
(IR intensity = 0.12)
(Raman active) 1327 cm-1
(IR intensity = 0.0034)
(Raman active)
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