Percent Yield

Percent Yield is the percentage of a compound formed when compared to the theoretical yield. This happens because of human error, side reactions, and impurities in the chemicals. Using Percent Yield you can figure if a certain Ion was used for the reaction, such as when Iron and Copper Chloride react, and two possible Ions of Iron can form. We used this to figure out the Ion of Iron in the Magic Lab. The formula and a short summary of is uses are shown here:

Here some guys go over Percent Yield and finding and interpreting it.