Humboldt State University ® Department of Chemistry

Richard A. Paselk

SA 560B; 826-5719

Final Exam Study Guide

Spring 2013 version

The Final Exam will be Comprehensive!

Approximately 1/3-1/2 will focus on recent material and those things you need to know to understand latest material, while the remainder will be on materials from previous Exam 1 Study Guide and Exam 2 Study Guide.

The Final will consist of multiple choice questions as well as a few problems with partial credit focused on the material covered since the last exam - check out the on-line sample to see the types and distribution of question types etc.

Review

Homework since Exam II (see suggested problems on Schedule). Review Quizzes (see Keys on my Moodle site), particularly those on materials since exam II. Review nomenclature so that you can read questions and understand them. Review concepts from exams I & II that we have used in looking at additional systems etc.

Be able to convert numbers to scientific notation and use numbers expressed in scientific notation; do all calculations with proper significant figures; make all conversions within the metric system (SI).

Chemical Bonding (Chapter 8)

What is electronegativity? How is it used? Be able to use electronegativity (both quantitatively and qualitatively-hi,lo rules) to predict the ionic/covalent nature of a bond.

What is an ionic bond? How is it formed? What forces maintain it? Anion. Cation. Ion pair. Be able to apply the octet rule to guess the ionic forms of the various "A" group elements. Why are outer electron shell octets so stable? What is a covalent bond? How do ionic and covalent bonds differ? How is it possible for an ionic bond to be "strong" and unstable while a covalent bond may be stable while not being as "strong"? How are electrons arranged in each?

What is a Lewis Structure? What is it intended to show? For which elements are Lewis structures most useful? (A groups) Be able to draw Lewis structures for all the A-group elements in their atomic and predicted ionic forms. Kernel vs. inert gas core.

Be able to draw a correct Lewis structure for any covalent molecule made up of atoms from the "A": groups. (Remember-you use Electronegativity to determine covalent or ionic first!) When do you need to use multiple bonds? Resonance? Are multiple bonds real? What does resonance represent in the real molecule? Be able to make proper resonance based sets of Lewis structures. For which A-grp elements does the octet rule not hold? (H to B) When is valence expansion required? Be able to draw correct expanded valence shell Lewis structures. Which orbitals are involved in expanded valence shells? What is the outermost shell of an atom? Does the outer-most shell of an atom need to have any electrons in it? Polar vs. non-polar bonding. Be able to assign Formal charges to each atom in a molecule. What are Formal charges useful for? Be able to predict chemical stoichiometry using Lewis structures, and balancing.

Bond dissociation energy. Bond length. Understand/be able to explain the energetics of ionic reactions. Be able to do a Born-Haber calculation given appropriate data. (In other words, you need to be able to recognize the required steps.) Understand/be able to calculate reaction enthalpies (H) given bond energies. How does bond length vary with multiple bonding?

VSEPR Theory (Chapter 8)

What is VSEPR theory? Be able to use the VSEPR method to determine the geometry of a molecule, including demonstrating the process involved-what assumptions are made with this model. Know the various orientations of electron pairs around a central atom and the various molecular geometry's they predict (handout in Discussion manual, p LN-4). What relations are there between electronic configuration and molecular shape? Does a given electron configuration always give the same molecular shape? Explain. Polarity: Be able to determine whether a given bond is polar or not. Be able to determine whether a given molecule is polar or not. Defend your decision (think charge separation [differences in electronegativity] and geometry). See also VSEPR Theory and Molecular Geometry Module

Solids (Chapter 10)

What is a solid? crystal? glass? How do we know about the detailed structures of solids? Be able to solve simple problems using the Bragg eqn. What is a lattice? a unit cell? Know the three cubic unit cells. How many "atoms" are there in each? Be able to solve simple density and volume problems involving unit cells (e.g. an element which forms crystals with a simple cubic unit cell has an atomic radius of x.xx, what is its density?). What is close packing?

What kinds of bonds and forces hold solids together? What are van der Waal's forces? London dispersion forces? Hydrogen bonds? Dipole-dipole bonds? Be familiar with the various types of solids (molecular, ionic, covalent metallic), their characteristic properties, and how these correlate with the bonds/forces holding them together. Sublimation.

Energy of Formation: How is it calculated? What is lattice energy? How is it calculated? Heat of crystallization. Bond Energies and Enthalpies of Reaction - Be able to calculate enthalpies of reaction given bond energies.

Liquids (Chapter 10)

Define/describe: weak forces, Hydrogen bonds, vapor pressure, phase change, boiling, solid,. Why is water's boiling point so high (vapor pressure so low)? How does it compare to other molecules? Are there any molecules with similarly high boiling points? Why do liquids boil? When? Why are boiling points lower in the mountains? Explain cooling by evaporation. Molar heats of vaporization and condensation. What is supercooling? superheating? Why do they occur? What is bumping? a seed crystal? Explain sublimation, triple point critical point. Equilibrium vapor pressure.

Solutions (Chapter 11)

Define/describe: solution, salt, solvent, solute, saturated solution, unsaturated solution, super saturated solution, mass %, ppm, ppb, molarity (M), molality (m), mole fraction (X), neutralization, equivalent (in chemical reactions). Why do some substances dissolve in each other? Why do others not? ("Like Dissolves Like").

How does solubility vary with temperature? Why? How does the solubility of gases vary with pressure? Explain this variation. What is Henry's law? Raoult's law? Ideal solution. What does each relate to? How are they different? What are colligative properties? What do they depend on?

Chemical Equilibria (Chapter 13)

Le Chatelier's Principle-be able to use it to guess outcomes with equilibria. Precisely define it as well. What do we mean when we say that chemical equilibria are dynamic? Define the equilibrium state briefly and precisely. Think about how systems, starting from different initial conditions approach equilibria. What is the "mass action expression"? Define Q. How is Q different from K, the equilibrium constant? When are they equal? Is an equilibrium constant "constant" at different concentrations? at different temperatures? What is the equilibrium condition? How is Kp related to Kc in the case of gases. Gases. Do K's have units? What is a homogeneous equilibrium? Heterogeneous equilibrium? Be able to solve problems involving both. What is the relationship between values of Keq for forward and reverse reactions? Be able to solve equilibrium problems like the examples we have seen in class. When are approximations legitimate? What assumptions are involved? Be sure you note assumptions. Be able to use quadratic equation if necessary. See also: Chemical Equilibrium Module

Acids & Bases; Acid-base Equilibria (Chapter 14–15)

Electrolytes. Dissociation. What is meant by "strong" and "weak" in reference to electrolytes, acids and bases? Degree of dissociation. Aqueous Solution Reactions: Be able to define acids and bases by the Arrhenius, Brønsted-Lowry, and Lewis definitions. What do we mean by conjugate acid and/or conjugate base in the "Brønsted" definition. What are the meanings of "strong" and "weak" for acids and bases by these definitions? What are precipitation and complexation reactions? Be able to write net ionic equations! Be familiar with classification scheme for reactions, solubility rules and strengths of electrolytes. What is Kdiss? Ka? Kb? Ki? Be able to write K's for acid/base reactions in both the Arrhenius and Brønsted-Lowry formulations. Be able to solve all manner of acid/base equilibrium problems. % dissociation problems. Polyprotic acids. What is an ion product? Know the ion product (Kw = 1.0 x 10-14) for water. Chemical Dissociation Equilibria Module

pH: What is pH? Define it. be able to solve pH problems. What is the relation of pH to pOH? What is the pH of a neutral solution? salt solutions? What does this depend on? Hydrolysis problems-what is going on here? What is Kh? What is its relationship to Ka and/or Kb? Correlate the Kh expression with chemical equation. Why are the various terms where they are?

Titrations: Be able to draw and interpret titration curves as we have seen in class and lab. Be able to find the equivalence point, buffer range, Ka or Kb and to identify the acid and base species in solution at any point along the curve. What is an indicator? How does it work?

Buffers: What is a buffer? Define precisely. Be able to do buffer problems. How can you make a buffer? See also pH and Buffer (Acid/Base Equilibria) Module

You may bring one-half sheet of 8.5 x 11 paper (8.5"x5.5") with any information you like on both sides (93.5 square inches) as a "cheat sheet" for the final.

You should be careful and thorough in designing and creating this sheet.

Remember it is for reference and insurance, the less you rely on it the better off you will be!

Note also that you will be provided with the Periodic Table and the equtions and constants sheet posted on Moodle.


 

Syllabus / Schedule

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© R A Paselk

Last modified 3 May 2013