problem 1: A 1.0 x 10-4 M solution of an absorbing compound, ex: benzene is placed in a rectangular cuvette with a path length of 1.0 cm. The absorbance of the solution is found to be 1.0.
a) Compute the compound's molar extinction coefficient, ?.
b) What fraction of the incident light exits the cuvette?
c) Compute %T if the concentration is doubled.
problem 2: Find out the given quantities for a Li+2 ion in a 4f state:
a) Its energy.
b) Its ionization energy.
c) Its rms (root mean square) radius.
d) Its orbital angular momentum, L, in units of h/2π.
e) Its degeneracy, that is, the number of distinct quantum mechanical states which have the same energy AND values of n and l
f) The number of different wavelengths of light emitted by a population of these excited species. Give the initial and final values of n for each transition.
problem 3: Draw the Lewis electron-dot structures of the 5 isomers of C2H5N. Predict the bond angles in each isomer. None of the structures will encompass atoms with formal charge.
problem 4: Consider the hydrocarbon allene which has the structural formula H2C=C=CH2.
a) Draw the Lewis dot structure of allene.
b) Find out the hybridization of all atoms.
c) Give an explanation of each unique bond in the molecule. Use the σ, π formalism.
d) Is allene completely planar? Support your answer with a brief discussion.
problem 5: Draw the Lewis-dot structures of 4 structural isomers of C3H4O. Are any of your isomers planar? Describe why. Would MO theory give a better treatment of any of your isomers? Describe why. Provide the given information for each isomer.
a) The hybridization of the heavy atoms.
b) Estimates of the bond angles.
c) Explanation of the bonds between the heavy atoms.
problem 6: Consider the structures of methane (CH4) and chloroform (CHCl3).
a) Which molecule has a rotational (microwave) spectrum? Why?
b) The atmospheres of the outer planets have a high concentration of methane. Would the presence of methane prevent mapping the surface of such planets with radar? Describe.
c) Which molecule has an infrared spectrum? Describe why.
problem 7: The conformers of 1,2-difluoroethane, the structural isomer of C2H4F2 in which the fluorine atoms are on separate carbon atoms. Which conformer the anti (s-trans) or the gauche, has a microwave spectrum? An infrared spectrum? An electronic spectrum? Describe. What chemical information can be obtained from the spectra?