Analysis of the Iron Complex Salt for Iron
Chemistry 112
Experiment 3: Analysis of the Iron Complex Salt for Iron:
Titration with EDTA
Introduction:
The lab to analyze of iron complex salt was a series of three labs. On this last lab, we analyzed the iron oxalate complex by using chelometric titration method. On the previous two labs we synthesized a complex of iron (III) () and oxalate () to prepare a salt precipitate and also quantitatively analyze the salt for oxalate. This lab was the final step that was required to determine the formula of the complex ion
For this chelometric titration, we use EDTA anion to titrate . this EDTA anion reacts with a metal ion (Me) forming a 1:1 metal chelate complex.
Me + EDTA Me(EDTA)
After that by using finding the volume and molarity, we easily calculated the number of moles of iron present in the sample that we prepared on our first lab.
Procedure:
First we transferred about 0.4g of complex salt transferred into a Erlenmeyer flask. Then we added H2SO4 into the flask and heated it to decompose and convert to CO2. After that, the solution was cooled down, we carefully added 15mL water to wash down the sides. Then again we heated the solution until its clear. After the solution was cooled down we added sodium acetate to it. We standardized the pH of the solution between 2.0 to 2.4 by using NaOH as a buffer. Once we adjusted the pH, we added salicylic acid to it. Then we warmed the solution was warmed to 55C and titrated with EDTA. We reached the end point of the titration when it turned into a clear yellow. The whole process was repeated for two more times to achieve more accurate results. At the end, we calculate the moles Fe3+ per gram of salt in each sample from the moles and volume of EDTA and the weight of the sample. And finally from using the the moles and per gram of salt we were able determine the formula of complex salt of iron
Data
Sample 1 |
Sample 2 |
Sample 3 | |
Weight of complex ion salt used |
0.403g |
0.406g |
0.401g |
Final buret reading |
15.71mL |
30.21mL |
46.91mL |
Initial buret reading |
0.01mL |
15.71mL |
30.21mL |
Volume of EDTA used |
15.70mL |
14.30mL |
16.70mL |
Molarity of EDTA |
0.05M |
0.05M |
0.05M |
Results
Sample 1 |
Sample 2 |
Sample 3 | |
Moles EDTA used in titration |
7.85moles |
7.25moles |
8.35moles |
Moles in sample |
7.85moles |
7.25moles |
8.35moles |
Moles per gram of salt |
1.95moles/g |
1.79moles/g |
2.08moles/g |
Average moles of per gram of salt |
1.95moles/g |
Average moles of per gram of salt |
6.51 moles/g |
Ratio of moles / |
3 |
Formula and charge of complex ion |
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