Chemistry Answers

Estimate the orbital energies to use in a calculation of the molecular orbitals of HBr. For data, see Tables 8B.4 and 8B.5. Take β = −1.00 eV.

A reasonably reliable conversion between the Mulliken and Pauling electronegativity scales is given by eqn 9D.4. Use Table 9D.1 in the Resource section to assess how good the conversion formula is for Period 3 elements.

Estimate the orbital energies to use in a calculation of the molecular orbitals of HCl. For data, see Tables 8B.4 and 8B.5. Take β = −1.00 eV.

A reasonably reliable conversion between the Mulliken and Pauling electronegativity scales is given by eqn 9D.4. Use Table 9D.1 in the Resource section to assess how good the conversion formula is for Period 2 elements.

The languages of valence-bond theory and molecular orbital theory are commonly combined when discussing unsaturated organic compounds. Construct the molecular orbital energy level diagrams of ethene on the basis that the molecule is formed from the appropriately hybridized CH2 or CH fragments.

Use an appropriate semi-empirical method to compute the equilibrium bond lengths and standard enthalpies of formation of (a) ethanol, (b) 1,4-dichlorobenzene. Compare to experimental values and suggest reasons for any discrepancies.

Solve the following problems using the correct format. Given first, what is asked for, and the formula together with the solution. 

1. A gas occupies a volume of 400 cm³ at a pressure of 2.00 atm. What would be the new pressure if the volume is increased to 500 cm³ ?
2. The volume of a given gas was 50 cm3 at 260C. After heat was applied to the gas, its volume increased to 80 cm3 . If the pressure was held constant, what is the new temperature of the gas? 

Set up the secular determinants for cyclobutadiene, benzene, and cyclooctatetraene and diagonalize them by using mathematical software. Use your results to show that the π molecular orbitals of monocyclic polyenes with an even number of carbon atoms follow a pattern in which:

• The π molecular orbitals of lowest and highest energy are non-degenerate.

• The remaining π molecular orbitals exist as degenerate pairs.

Suppose that a molecular orbital of a heteronuclear diatomic molecule is built from the orbital basis ψA, ψB, and ψC, where ψB and ψC are both on one atom (they can be envisaged as F2s and F2p in HF, for instance). Set up the secular equations for the optimum values of the coefficients and set up the corresponding secular determinant.