Chem 125  Fall 2004

Study guide for midterm Exam #1

 

The exam will be held Thursday October 14, in BI 212, from 6 pm until 8 pm.  Bring a calculator.  Partial credit for multi-step problems will be given ONLY if you show your work.  In some cases full credit will not be given UNLESS you show the logical progression of your work.  Some of the problems are designed to test your ability to solve chemical problems (such as those in Atkins and Jones, the pre-labs, and quizzes).  Other questions will be designed to test your understanding of the chemical concepts discussed in lecture.  Equations (e.g. E = hn), constants (e.g. Planck’s constant etc.), a summary of solubility rules, a table of electronegativity values, and a “bare bones” periodic table will be given to you.

 

- Lecture on 10/14 will be an optional review/Q&A session.  Come prepared with your questions.

 

The exam covers primarily the material in the “Fundamentals” section and Chapters 1 and 2; however, an understanding of concepts from the lab exercises is also expected.  This list is not guaranteed to be comprehensive, but it is a very good idea to review the following topics in preparation for the exam.

 

General:

You should be familiar with the following:

1) mass relationships (density; % mass by weight)

2) basic stoichiometry

balancing equations

calculating formula weights/molar masses (review lab #2)

identify the limiting reagent in a reaction (see quiz #1)

3) calculation of molar concentrations (review lab #1)

4) dilution and titration problems (review lab #1)

5) calculation of light energy from frequency or wavelength data

6) determination of differences in orbital energies from wavelength or frequency data

7) drawing diagrams of emission and absorbance events

8) predicting which atoms are larger, or have higher ionization energy than others

9) identifying valence electrons for atoms and ions and predicting charges on ions

10) ground state electron configurations for atoms and ions

            paramagnetic vs. diamagnetic ground states

11) drawing satisfactory Lewis diagrams, including resonance structures

12) using formal charge calculations to identify favored resonance structures (see quiz #2)

13) predicting whether a reaction forms a precipitate (review lab #3)

 

Your answers must ALWAYS have the appropriate units!

 

Concepts to study:

Molarity concepts

            - molarity = (mol of solute)/(liters of solution)

            - molar concentration calculations

            - dilutions: M1V1= M2V2

            - titrations: (reaction stoichiometry) * M1V1= mol of solute

 

Types of chemical reactions

- determination of net ionic equations (use of solubility rules); predicting precipitate formation

 

The Bohr model of the atom

            - calculating wavelengths/energies of line spectra

            - calculating differences in energy levels

                        Rydberg equation

            - know the visible region of the spectrum (400-750 nm); which is the “red” part of the spectrum?; which is “blue”?

 

The quantum mechanical model of the atom

- the roles played by Planck, Einstein, Rydberg, Bohr, Heisenberg and Schrödinger in the historical development of quantum mechanics (see “overview of development of QM” handout given in class)

            - what is an “orbital”?

- how do the nuclear model, the Bohr model and the quantum mechanical model differ?

- how do the quantum numbers “n” and “l” determine the energy of an orbital?

- shapes of s, p, d orbitals

- calculations of differences in orbital energies

            Particle in a box model

 

Aufbau (building up) 

- organization of periodic table as it relates to electronic structure of the atom

- Pauli Exclusion principle

- Hund’s rule

- valence electron configurations

 

Trends in the periodic table

- ionization energy

- atomic size (effective nuclear charge, shielding, Coulombs Law interpretation)

- electron affinity

 

Ionic bonding

            - predicting relative strengths of covalent bonds based on ionic radius/nuclear charge

            - bond formation releases energy

            - predicting chemical formula based on expected charges of ions (especially groups 1, 2, 13, 15-17)

                       

Covalent bonding and molecular structure

- Lewis diagrams

            octet rule

- electronegativity scale; polar covalent bonds vs. non-polar  bonds

 

 

Preparation Strategy:

- Work as many problems as you can (this works best after you have read the textbook).  Here are some specific suggestions for review problems from your text:

Problems from the “Fundamentals” section.

p. F12-13: A.25

p. F22-23: B.1

p. F29-30: C.1; C.5; C.7; C.11

p. F43-44: E.5; E.21; E.23; E.25

p. F48-49: F.3; F.7; F.13; F.19

p. F56-57: G.7; G.15; G.21

p. F60-61: H.5; H.11; H.17

p. F66-67: I.11; I.25

p. F72: J.3

p. F86-88: L.7; L.11; L.13; L.15; L.17; L.21

p. F93-94: M.3; M.5; M.11; M.17

 

Chapter 1: 3, 7, 13, 23, 27, 41, 43, 51, 53, 59, 61, 69, 73, 77, 83, 85, 97, 101 (note part of the answer to #27 is incorrect!)

 

Chapter 2: 3, 7, 13, 15, 19, 23, 29, 31, 33, 35, 39, 43, 47, 49, 53, 55, 63, 69, 71, 75, 85, 91, 93, 99, 103 

 

- Review pre-lab questions and calculations performed in the labs.

 

- Review the quizzes and make sure you can solve all the questions.