Chapters 8, 9, and 24 Exam Review

Below this written is a key for all of the questions /problems presented in the review for the Chapters 8, 9, and 24 test. All of the concepts on the test are not covered by the review packet. I will list the topics not covered in the review packet so you can look at other materials from the unit of study. The test will consist of 35 multiple choice questions and 5 short answer questions. You will be supplied a periodic table (the one given for the AP Chemistry exam) and I will give you a electronegativity table, though one would not be supplied on the AP Chemistry exam. You will also be able to use a calculator. The multiple choice test will be given on Wednesday, November 9th, 2011 and the short answer will be given on Thursday, November 10th, 2011.

I have supplied more information than what is needed in the answers to the key below. I was more in-depth than what would be needed on the exam because I wanted to use the study guide and key as one last teaching tool. When answering an AP Chemistry free response question: (1) Do exactly what is asked to do. (Draw a Lewis structure, etc.) (2) Make sure to compare and contrast if asked to do so. (3) Any term used in the answer should be defined.

WHAT TO STUDY

Know how to define (non-polar) covalent, polar covalent, and ionic bonds and understand the mechanisms of how each is made.

You need to know from memory all parent geometries, molecular geometries, and bond angles. Know the criteria for each.

Know the concept of lattice energy and that the magnitude of lattice energy is dependent upon the magnitudes of the ion charges and the distance between the nucleus of both ions in the bond. For a large lattice energy, large charge magnitudes and small ion distances are needed. For a smaller lattice energy, small charge magnitudes and large ion distances are needed. L.E.=k(Q1Q2)/d.

Know all criteria for hybridized orbitals. On a previous blog post, all of the criteria and applications were written out.

Know how to determine the enthalpy (heat) of a reaction from the energy inputs (i.e. heat of sublimation, bond energy, ionization energy, etc.) and energy outputs (electron affinity, lattice energy). If energy inputs exceed energy outputs, a endothermic reaction will occur. If energy outputs exceed energy inputs, a exothermic reaction will occur.

Know how to choose the most plausible Lewis structure based upon formal charge. Zeros are preferred and the more electronegative element should be a negative number is not zero. Also, all formal charges must add up to the total charge of the molecule.

Know the basic concept of isomers. This is covered in its most basic form on page 1026 of your book at the very beginning of section 24.4. This concept is covered in the review from the year 1994, question #43. An isomer is a molecular formula that can have more than one Lewis structure that works for the number of atoms in the molecule. This is not to be confused with resonance structure, which is just the moving of a double or triple bond. This is completely different positions of atoms within the molecule with different types of bonds to achieve the different atom positions. I have given an explanation on the review.

Know how to define and recognize a Lewis acid and a Lewis base.

Know the rule to determine the coordination number of a Lewis acid is to double the oxidation (charge) number. The coordination number will be the number of ligands (Lewis bases) that will surround the Lewis acid (metal ion) in the middle of the complex ion.