Redox Titration
Introduction
In this experiment you will determine the molarity of iron (II) in an unknown solution. This experiment will be done using the titration method. This is an example of a redox reaction involving the following unbalanced equation:
____ H+ + ____ MnO4- + ____ Fe2+ ® ____ Mn2+ + ____ Fe3+ + ____ H2O
Prelab Assignment: Balance the reaction shown above in acidic solution.
SAFETY: The permanganate solution is corrosive. If you get it on your skin, wash it off immediately. If you spill it on your clothes, wash it off. It may leave a stain.
Experimental - Determination of the Fe2+ Content of an Unknown Solution
1. Obtain approximately 50 mL of potassium permanganate solution in a beaker. Record the molarity of the permanganate solution on your report sheet. Use this solution to fill your buret.
2. Obtain approximately 25 mL of the unknown iron solution in a beaker.
3. Transfer 5 mL of the unknown iron solution into an Erlenmeyer flask using a graduated cylinder. Add one plastic pipet full of phosphoric acid and 40 mL of deionized water (use a graduated cylinder here) to the Erlenmeyer flask containing the unknown iron solution.
4. Titrate the sample with the permanganate solution making sure to record the initial and final buret volumes. The endpoint of the titration is when the pink color PERSISTS for AT LEAST 20 seconds in the flask.
5. Repeat steps 3 – 4 three more times.
Analysis
1. Using the volume of permanganate solution, the permanganate ion concentration recorded from the container, and the balanced chemical reaction, calculate the molarity of the unknown iron (II) solution for each trial.
2. Calculate the average for the iron (II) molarity.
Redox Titration
REPORT SHEET
Name:______
Lab Partner:______
Date: ______
Determination of the Fe2+ Content of an Unknown Solution
Molarity of Permanganate Ion Solution (from the bottle) ______M
Trial / mL of unknown Fe2+ solution used / Initial volume of MnO4- (mL) / Final volume of MnO4- (mL) / Volume of MnO4- used (mL) / Molarity of Fe2+ (M)1 / 5.00
2 / 5.00
3 / 5.00
4 / 5.00
Average Molarity of Fe2+ ______M
Show calculations below: