Assessment of Spartan AP Chemistry students Julie B. Ealy Haverford College – to be PSU ACS – April 2001 Bond length and effect of atom size on bond length Dipole and lack of a dipole Bond angle and effect of atom size on bond angle Orbitals involved in bond angles Single, double, & triple bonds: bond length and bond energy Lewis dot structure, electrostatic potential surface, and dipole Conformation and stabilization of a molecule Ketone, alkane, and alcohol – intermolecular forces, molecular geometry, and hybridization Expanded octets and hybridization Question 1. Provide a formula for Structure 10 and explain how Structure 10 and Structure 13 are related by discussing the colors on the electrostatic potential surface and providing a Lewis dot structure for Structure 10. Be concise. Question 2. Structure 5 has a dipole and Structure 6 does not. Explain what a dipole is and why there is a difference in the two structures. Question 3. On Structure 6 the bond length between the central atom (carbon) and the atom at the top of the structure (hydrogen) is shorter than the bond length in a similar position on Structure 3. Explain the difference. Question 4. The bond angle in Structure 2 (NH3) is approximately 107o for H-N-H. In Structure 4 which represents PH3, the H-P-H bond angle is approximately 93o. Explain the difference in terms of the orbitals used for bonding. It is not necessary to draw an orbital representation, but do explain the difference. Question 5. Rank structures 19, 21, 23, and 24 in terms of bond length between two carbons from shortest to longest bond length. Also indicate the bond energy between two carbons using the following values in kJ/mole for structures 19, 23, and 24: 346, 615, and 825 (NOT respectively). Provide an educated estimate for Structure 21. Provide an explanation for the C-C bond that is the strongest. Question 6. Structures 22 and 23 are two different views of the same molecule. Provide an explanation as to why Structure 23 would have adopted the conformation it did when the structure was minimized utilizing Spartan. Question 7. Structures 37, 38, and 39 represent a ketone, alkane, and alcohol. Identify each structure by the organic group to which it belongs. Indicate the type of intermolecular force(s) for each organic group. Question 8. Provide the molecular geometry and hybridization around the atom marked with an arrow on Structures 37, 38, and 39. Question 9. Structures 25, 26, and 27 are all linear. The following molecules are represented: HgBr2, BeCl2, and XeF2. Provide two chemical reasons how you know which structure is XeF2. An explanation utilizing color of the atoms is not sufficient. Which hybrid orbitals were utilized for the xenon and how many lone pairs are there around xenon? Structures 25, 26, and 27 for Question 9. Which structure is XeF2 and why?