This page is a basic exercise in writing skeletal redox equations from descriptions of the process. Since the page has to read four strings correctly, you need to be very careful with your input.
Enter the compounds in the sequence OA + RA => RA + OA
Although it is not standard, for charged species enter the sign of the charge followed by the number as in Fe+3. If it is singly charged, leave off the "1" (Na+)
Do not be concerned about any balancing or stoichiometry.
The javascripting that powers this practice problem generator was produced by Professor George Wiger of California State University Dominguez Hills.