***SHOW ALL WORK FOR POINTS USING MY NUMBERS*** An Erlenmeyer flask from the pre
ID: 843172 • Letter: #
Question
***SHOW ALL WORK FOR POINTS USING MY NUMBERS***
An Erlenmeyer flask from the previous experiment containing the solution of the iron-oxalate complex after the titration with potassium permanganate was retained. The mass of the iron-oxalate complex used in this titration was 0.1504 grams.
The solution was made up to 250 mL exactly, and then 20 mL of the solution was ultimately diluted to exactly 100 mL. Thiocyanate was added to produce a deep red color and the absorbance of the solution at 450 nm was measured.
According to the calibration curve, the absorbance corresponded to a concentration of Fe3+ equal to 2.449E-4 M.
1. What is the concentration of Fe3+ in the 250 mL flask?
2. Moles of Fe3+ in the 250 mL flask?
3. Mass of Fe3+ in the 250 mL flask (g) ?
Calculate the mass percent of iron in the complex.
4. Percent iron in the complex = ???%
A 0.5082 gram sample of the iron oxalate complex was heated in an oven at about 75oC for 60 minutes. Upon cooling and reweighing the sample, it was determined that the mass lost was 0.0561 grams.
5. What is the percent by mass of water in the iron-oxalate complex?
6. If the percent by mass of oxalate in the complex had previously been determined to be 51.78%, what is the percent by mass of potassium in the complex?
***SHOW ALL WORK FOR POINTS USING MY NUMBERS***
Explanation / Answer
1) Concentration of Fe3+ in the 250 mL flask = M
= 2.449 * 10-4 M * (5) = 1.22 * 10-3 M
2) Moles of Fe3+ in the 250 mL flask = mol
= 1.22*10-3 * 0.25 = 3.05 * 10-4 mol
3) Mass of Fe3+ in the 250 mL flask = gram
= 3.05 * 10-4 * 55.85 = 0.017 gm
4) Percent iron in the complex = %
= (0.017 / 0.1504) * 100 = 11.3 %
5) Percent water in the complex = %
= (0.0561 / 0.5082) * 100 = 11.03 %
6) Percent potassium in the complex = %
= 100 - 51.78 - 11.3 - 11.03 = 25.89
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