Chemistry
Chemistry 19: 1-3
Homework
Voltaic Cells
Chapter 19: 1-3 Homework
- Reading Preparation
- WebLecture
- Study Activity
- Preparation work for chat
- Online Quiz
- Lab Instructions
Reading Preparation
Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 13: Sections 1 to 3.
Study Notes
- 19.1 In oxidation-reduction reactions, we can break the reaction into its oxidation component and its reduction component, and account for the transfer of electrons in each "half-reaction". This method allows us to balance the overall reaction, since the net exchange of electrons must not introduce or lose electrons.
- 19.2 In a simple voltaic cell, two half-cells contain the oxidation and reduction reactions respectively, but the ions produced can move freely from one cell to the other through a connector (often a salt bridge or semi-permeable membrane). Metal electrodes carry the current through the remaining segment of the circuit. The electrodes may or may not participate in the reactions by supplying electrons or ions to the system.
- The electrode at which oxidation occurs is the anode (note both terms start with vowels).
- The electrode at which reduction occurs is the cathode (note both terms start with consonants).
- 19.3 Commercial voltaic cells include all common household batteries. Primary batteries are dry cells and alkaline batteries that cannot be recharged after they are discharged. Secondary batteries such as those used in cars and most electronic devices can be recharged by reversing the flow of electrons through the battery.
Key Formula
| Reaction | Example | Notes |
|---|---|---|
| Overall Reaction | M(s) + N+(aq) → M+(aq) + N(s) | Solid metal transfers electron to ionized metal in solution. |
| Oxidation Half Reaction | M(s) → M+(aq) + e- | Atom gives up electron |
| Reduction Half Reaction | N+(aq) + e- → N(s) | Ion takes on electron |
Read the following weblecture before chat: Oxidation Reduction Reactions and Voltaic Cells
Study Activity
Videos for Chapter 19: Principles of Chemical Reactivity: Entropy and Free Energy
Review the Videos at Thinkwell Video Lessons.
- Under "ELECTROCHEMISTRY"
- Principles of Electrochemistry
- Reviewing Oxidation-Reduction Reactions
- Galvanic Cells
- Electrochemical Cells
- Electromotive Force
- Principles of Electrochemistry
Go to the AACT Galvanic Cells experiment.
- Click on start.
- For the first experiment, set up copper in the left beaker and zinc in the right beaker.
- Click the off button to turn current "on".
- Click "See Molecular Scale" on each beaker and on the salt bridge.
- Observe the following:
- What is the direction of electron flow in the anode (black) and the cathode (red)?
- At which node does oxidation occur? Reduction?
- What is the change in mass of each node?
- What is the half-reaction at each node?
- Where do negative ions from the salt bridge wind up?
- Where do positive ions from the salt bridge wind up?
- What is the purpose of the salt bridge?
- If you make a new voltaic cell with Zn and Ag electrodes, which will be the anode? Which the cathode? Why?
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
Chapter Quiz
- There is no chapter quiz YET.
(Aligns to) AP LAB #16 GUIDED INQUIRY — — Building an Electrochemical cell — Phase I
Identify target battery cell criteria, then design a chemical (wet) battery cells, noting all materials required. You will build the cell and calibrate its output in the next phase, then use your batteries (or commercial batteries) to observe the results of electrolysis on common molecules and rank results.
Resources:
- AP2009 20 Determination of Electrochemical Series
- AP2009 21 Measurements using electrochemical cells and electroplating
- IGHCE Lab 16.1 OR HSCKM X-1 Produce Hydrogen and Oxygen by Electrolysis of Water
- IGHCE Lab 16.2 OR HSCKM X-2 Observe the Electrochemical Oxidation of Iron
- IGHCE Lab 16.3 OR HSCKM X-3 Measure Electrode Potentials
- IGHCE Lab 16.4 Observe Energy Transformation
- IGHCE Lab 16.5 OR HSCKM X-4 Build a Voltaic Cell
- IGHCE Lab 16.6 Build a Battery
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