Iron (II) or (III) Determination

Introduction

In this experiment we will use stoichiometric principles to deduce the appropriate equation for the reaction between metallic iron and a solution of copper (II) sulfate. This reaction produces metallic copper, which is seen precipitating as a finely divided red powder. This type of reaction, in which one metal "displaces" another from a solution of one of its salts, is known as a single replacement reaction. A metal capable of displacing another from a solution of one of its salts is said to be "more active" than the displaced metal. In this experiment, iron is more active than copper. 

Iron forms 2 types of ions, namely Fe+2 and Fe+3. We shall use stoichiometric principles to determine which of these ions is formed in the reaction between iron and copper (II) sulfate solution. If Fe+2 is formed, then equation (1) is correct, while equation (2) is correct if Fe+3 is formed. Your task is to find out which equation is consistent with the results of your experiment.

    (1)        Fe(s) + CuSO4 (aq) → FeSO4 (aq) + Cu(s) 

                Fe(s) + Cu+2(aq) → Fe+2(aq) + Cu(s) 

    (2)       2 Fe(s) + 3 CuSO4 (aq) → Fe2(SO4)3 (aq) + 3 Cu(s) 

               2 Fe(s) + 3 Cu+2(aq) → 2 Fe+3(aq) + 3 Cu(s)

An excess of copper (II) sulfate solution (to make sure that all the iron is reacted) will be added to a known amount of iron. The metallic copper produced will be weighed. These weighings will be used to calculate the moles of iron used and the moles of copper formed. If equation (1) is correct, the moles of copper should equal the moles of iron. If equation (2) is correct, we should obtain 1.5 moles of copper per mole of iron.

Pre Study

View Pre-Study document here. These questions will prepare you for the type of analysis that you will need to do as part of the lab. If you are comfortable with the pre-study document you should be prepared to do this lab on your own! 

*Answers to the pre-study document is provided in the Complete Lab Guide (below).