
Abstract 1. Introduction Redox chemistry is, however, generally one of the most difficult subjects for students, who often have trouble applying the given rules to specific problems. To master the subject, students need to work through a number of practice problems themselves. The more they practice, the better they understand what they are doing. But a key to their success is that they be given consistent feedback on their work. Our experience has shown that immediate and wellthought out feedback can be of significant benefit in helping students master redox chemistry. 2. Goals We decided to develop an interactive online tutorial as a learning aid for the students. The goals for the tutorial were:
Every subtopic includes both a tutorial and a practice problem set. The tutorial uses examples to demonstrate the application of the rules. The problems give the students plenty of practice with instantaneous feedback on their answers, so the students know whether their approach to the problems is correct. 3. Program Design
and Usage The tutorials were developed based on the lecture notes written by Dr. Angela King. Notes were modified to show how material would be presented in class. These stepwise notes, coupled with comments on design, were used as the basis for the tutorials. 

Figure 1. A section of the storyboarding based on the lecture notes of the balancing redox reaction tutorial. 
3.2 Practice Problems 3.2.1 Assigning Oxidation Numbers Three questions are randomly drawn at one time from a pool of problems. The student answers the questions by entering the oxidation number for each element in the formula. If the student does not get a question correct, a brief explanation for the wrong answer is given and the question appears again. To encourage the student to get the questions correct, a surprise bonus appears when the student gets all three questions correct in the same set. 


An external link to the authors' fullblown version of Identifying Redox Agents and Reactions. 
At first, we wanted to create a program to track students's progress at each step, but we soon realized that it would not be possible for the following reasons:
Since the students' common mistakes of balancing the redox equations are mostly mathematical, we decided that the program should provide two answer checkings: the final equation and the half reactions right before they are added together. The students have a choice to check if the half reactions are balanced. They do not have to check the half reactions in order to check the final equations. By checking the half reactions at midpoint in the process, students will know if they have miscalculated atom and charge counts of both sides of the half reactions, which is the cause of one of the common mistakes. If the half reactions are not balanced, the program will list out the agents that are not balanced. 

Figure 4. Partial screen capture of online exercises of balancing redox reactions to show the midpoint checking of the half reactions. 

