General Chemistry Multiple Choice Exam-“oxidation” and “reduction” mean.

EXAM 3 STUDY GUIDE

The exam will consist of 20 multiple choice questions with 70% “C” questions, 20% “B” questions, and 10% “A” questions. In general, “C” questions are those involving the most basic concepts, particularly ones that you have used before. “C” calculation problems typically involve one major step with 1-2 more minor steps. (Examples of minor steps would be calculating molecular weights or converting [H3O+] to pH.) “B” questions involve more difficult concepts, particularly ones that are new. “B” calculation questions typically involve at least two major steps with 1-4 minor steps. “A” questions are those involving the most difficult concepts or those that require a thorough understanding in order to answer correctly. Often “A” questions require bringing together different concepts to solve the problem and 2+ calculation steps. Note also that concepts listed under the “C” or “B” categories below can be converted to harder questions, depending on how I ask the question.

Background Concepts [Homework Examples]

  • Know the molecular formulas and charges of common ions. [Common Ion handout]
  • Calculate molar mass, convert between grams and moles using the molar mass. [Problem Set 1]
  • Calculate concentrations in molarity, convert between liters and moles using molarity. [Problem Set 1, Quiz 2]
  • Calculate concentrations after dilution. [Exp. 2]

“C” Questions [Homework Examples]

Chapter 17:

  • Know what “oxidation” and “reduction” mean.
  • Determine oxidation numbers; decide what is being oxidized and what is being reduced; identify oxidizing and reducing agents. [17.3, 17.7, 17.9, quiz 7’s]
  • Balance oxidation-reduction reactions in acidic or basic solution. [17.6, 17.8, quiz 7’s]
  • Understand the basics of how an electrochemical cell works. [exp. 6, S19 ex3a.9]
  • Know what “electrode”, “anode” and “cathode” mean.
  • Understand the shorthand notation for electrochemical cells. [17.13, 17.15]
  • Be able to determine the overall reaction occurring in a given electrochemical cell and vice versa:

construct an electrochemical cell in which a given oxidation reduction reaction will occur. [17.13,

17.15, quiz 8’s]

  • Calculate E°cell from E° values. [17.23, 17.25, 17.27, PS5, quiz 8’s]
  • Calculate ΔG° and K from E°cell and vice versa. [F20 quiz 7]
  • Use E° values to predict which in a series of compounds will be the best oxidizing or reducing agent.[quiz 8’s] Chapter 12:
  • Know the relationship between reaction rates for different reaction components. [12.3, 12.6, S20 quiz 8]
  • Know what the rate law, reaction order and rate constant are. [quiz 9’s]
  • Calculate k from rate law, knowing initial rate and concentrations. [quiz 9’s]
  • Calculate rate at particular reactant concentrations, knowing rate law and value of rate constant.
  • Determine rate law from initial rate data. [12.23, 12.25, quiz 9’s]
  • Use the integrated rate law for a first order reaction. [PS6, quiz 9’s,]
  • Use the integrated rate law for a second order reaction. [PS6, quiz 9’s]
  • Know how to distinguish between zero, first and second order reaction from concentration vs. time data using integrated rate laws. [12.33, 12.35, PS6, quiz 9’s]
  • Know how temperature affects rates.
  • Be familiar with the Arrhenius equation. Know what the frequency factor and activation energy represent and how they relate to the rate constant. What is the physical significance of the e Ea/(RT) fraction in the Arrhenius equation.
  • What is an elementary reaction according to collision theory?
  • According to collision theory, what 3 criteria need to be met in order for an elementary reaction to occur?
  • What is a unimolecular elementary reaction? What is a bimolecular elementary reaction? What is a termolecular elementary reaction? Why is a termolecular elementary reaction so unlikely according to collision theory?
  • Know the basic concept behind transition state theory and what the transition state represents.
  • Be able to construct and/or interpret a simple reaction coordinate diagram for an elementary reaction; know where the transition state is and how to determine Ea,f and Ea,r, ΔGrxn from the diagram. [S20ex3.18]
  • What is an elementary reaction according to transition theory?
  • Be able to construct and/or interpret a reaction coordinate diagram for a multi-step reaction and understand how it relates to the mechanism. [F19ex3a.12; S20ex3.19]
  • Know what the significance of the slow or “rate-determining step” in a reaction is.

“B” Questions [Homework Examples]

Concepts listed under the “C” category can be converted to B questions by combining them and/or requiring a better understanding of the concept in order to be solved.

Chapter 17:

  • Calculate Ecell under non-standard conditions using Nernst equation. [PS5, WS3, old quiz8’s]
  • Less straightforward problems using the Nernst equation, e.g. calculating concentrations from Ecell values. [PS5] Chapter 12:
  • Understand important concepts behind collision theory: What does the concentration term in the rate law of an elementary reaction represent? why does increasing the molecular size of a reactant generally lead to a decrease in reaction rates? What does the activation energy represent according to collision theory? Why do the rates of elementary reactions increase with temperature?

“A” Questions (Homework Examples)

Concepts listed under the “C” or “B” categories can be converted to A questions by combining them and/or asking the question in such a way that the route to the answer is not straightforward and requires a thorough understanding of the concepts.

Chapter 17:

  • Calculate K’s and ΔG°’s using E° values, and vice versa, harder examples. [F19ex3a.20] Chapter 12:
  • Understand the concepts behind “pseudo-order” reactions and how the integrated rate laws can be used to determine more complicated rate laws using pseudo-order conditions. [PS6, Exp. 7]

Information that will be given with exam:

Table of E° values.

Chapter 17 and 12 equations.

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