Module 4
1. Module 4
1.25. Page 2
Module 4—Batteries and Balance
Explore
Read
Earlier in this module you were asked to list similarities and differences between electric and electrolytic cells. One important similarity is that both cell types need a transfer of electrons in order for any chemical change to occur. You tested this when you constructed a voltaic cell and observed the change in the voltmeter reading when the cell's circuit was broken by briefly removing various components. In an electrolytic cell, you observed that a chemical change only occurs when the power source is turned on and a voltage greater than the minimum cell potential is applied. Is it possible to identify what chemical entity controls the change observed in other species? What do these observations tell you about electrochemical cells in terms of quantitative relationships?
You probably haven't considered electrons as quantifiable. However, when you wrote half-reactions, you used coefficients to indicate the proportions of electrons involved in an oxidation or reduction. Read the text and work through the “Sample problems” and “Communication examples” on pages 652–654 in the textbook to learn more about the methods used to quantify electrons.
Self-Check
SC 1. Complete “Practice” questions 1–4 on page 653 of the textbook and “Practice” questions 5–7 on page 654 of the textbook.
Read
In the previous section you learned how to use measurements of amperage and time to calculate moles of electrons. As you will recall, a balanced chemical reaction, including a half-reaction, provides information about the proportions of substances in a chemical process. With knowledge of the quantity of electrons, you will be able to complete the same kinds of stoichiometric calculations performed elsewhere in this course to determine the quantities of other species in the half-reaction.
Read pages 655–656 in the textbook. Work through “Sample problem 14.4” and “Communication example 3” to learn more about performing these calculations.
Self-Check
SC 2. Complete “Section 14.4” questions 1–3, 9, 11, and 12 on page 657 of the textbook.
Module 4: Lesson 5 Assignment
Retrieve your copy of the Module 4: Lesson 5 Assignment that you saved to your computer earlier in this lesson. Complete the Assignment. Save a copy of your completed Assignment in your course folder. You will receive instructions later in this lesson on when to submit your Assignment to your teacher.
Try This
Earlier in this module you investigated voltaic cells. Could the calculations involving amperage, time, and moles of electrons be applied to predicting the changes involved in the operation of a voltaic cell?
TR 1. Demonstrate the application of stoichiometry to predicting a quantitative relationship in a voltaic cell of your choice. The cell can be a cell described in the textbook or in other resources, or a cell with reactants of your choice. Your demonstration can be presented in a format similar to the “Sample problems” or “Communication examples” in the textbook.
Save a copy of your answer in your course folder. Submit a copy of your answer to your teacher for feedback.