CHM 203 EXAM 1: CLOSED BOOK NAME:______________________<?xml:namespace prefix =

Question

CHM 203                                  EXAM 1: CLOSED BOOK                  NAME:______________________<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

a.      Define the Pauli, Aufbau and Hund principles.

b.      Allocate electrons to labeled orbitals for the element phosphorus. You must show degenerate orbitals as appropriate.

c.       Explain, using the four quantum numbers why the periodic table shows 10 elements in each row of transition elements.

2.  Molecular Structure.

a.  Give the full Lewis structure (using the individual electron notation) for the molecules below, including formal charges where necessary.

            1.  methylamine (CH3NH2)

            2.  thionyl chloride (SOCL2)

b. Give the oxidation # for each atom in the molecule CH3COCH2NH2.

c.   Show the bond dipoles and the overall molecular dipole for the molecules.

            1. CH3Br

            2. CBr4

d. Give all the possible isomers for compound molecular formula C5H12.  Identify each isomer by its IUPAC name.

3. Distinguish between the three models of acidity/basicity, using example equations in your answer.

4. Use the LCAO-MO method to explain why a sigma bond is formed between two carbon atoms by sp3 orbitals. You must label the diagram fully. You must explain why a bond is formed.

5. For the hybridization of carbon:

            a.  Explain why this procedure was necessary to explain the equal C-H bond length found in methane.

            b. Explain the formation of sp, sp2, sp3 orbitals including the orbitals used and produced the shape of all orbitals discussed and the orientation of orbitals in each type of hybridization.

          c.   Explain why a sigma bond between carbon atoms can rotate but a pi bond cannot.

6. Chirality

            a. Explain how a polarimeter works.

            b. Explain how and why two enanotionmers can be separated.

7. Give diagrams of the possible chair conformers of cis 1,3-di-tertiarybutylcyclohexane, and indicate which is the energetically preferred state.

Explanation / Answer

Definition: The Pauli exclusion principle states no two electrons can have the identical quantum mechanical state in the same atom.

Hund's rule: which sttes that electrons spread out before they pair up if there are two or more energetically equivalent orbitals (e.g., p, d).

Definition: The Aufbau Principal simply put, means electrons are added to orbitals as protons are added to an atom.

The Aufbau principle outlines the rules used to determine how electrons organize into shells and subshells around the atomic nucleus.

Ans 6:

A chiral molecule is a type of molecule that has a non-superposable mirror image The feature that is most often the cause of chirallity in molecules is the presence of Asymmetric carbon atom..

Ans 6(a):

Ans 6(b)

http://chemistry.stackexchange.com/questions/153/how-do-you-separate-enantiomers

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