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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