What is the percent by mass of oxygen?

Idid a lab for chemistry where we put nails in a copper (ii) chloride solution. 1. why did the reaction stop? which reactant was used up? how do you know? 2. describe what was happening to the atoms of iron and copper during the reaction. what is this type of reaction called? 3. what would happen to the ratio of copper to iron if you had placed more nails in the beaker? if you had let the reaction go for less time? 4. what is the accepted ratio of copper atoms to iron atoms in this reaction? account for differences between your experimental value and the accepted value. write the balanced equation for the reaction.