Essay on Redox Titration Lab Report

750 Words Nov 12th, 2011 3 Pages
Determination of Fe by Redox Titration
Matt Cuff
Quant 320L
October 21, 2011

Abstract In this experiment the percent of iron in an unknown sample will be determined by using a redox titration and then compared to a different method. A primary standard which in this case is ferrous ammonium sulfate will be used to standardize potassium dichromate. The standardized potassium dichromate will then be used to titrate the unknown iron sample using the indicator p-diphenylamine sulfonate.

The standardized potassium dichromate which has a concentration around 0.017 M is then titrated into the unknown iron sample which is dissolved in deionized water. The unknown sample is titrated to its end point using the indicator p-diphenylamine
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Then use this information to calculate the percent iron in the unknown sample.

The only obvious observations that could be made in the experiment was the color change of the solution from green to purple due to the indicator p-diphenylamine sulfonate and also titrating the solution with potassium dichromate.

Data Analysis Trial 1 Trial 2 Trial 3 Trial 4
Wt. Fe(NH)2(SO4)2 , g 0.5025 g 0.5010 g 0.5003 g 0.5013 g
Vol. K2Cr2O7 , mL 13.72 mL 14.22 mL 13.83 mL 13.69 mL
Wt. Unknown , g 0.5020 g 0.5020 g 0.5022 g 0.5004 g
Vol. K2Cr2O7 , mL 9.07 mL 10.18 mL 9.53 mL 9.78 mL
% Iron in sample 10.29% 11.55% 10.85% 11.11%

Trial 1 10.29% Fe
Trial 2 11.55% Fe
Trial 3 10.85% Fe
Trial 4 11.11% Fe
Mean 10.95% Fe
STD ± 0.5% Fe
RSD ± 0.05% Fe

Calculations

[K2Cr2O7] = 0.017 M
9.07 mL K2Cr2O7 * 0.017 M = [pic]

Spooled =[pic]
Spooled = 9.20 tcalc = [pic] tcalc = 1.197
@ 90% ttable = 1.90 ttable > tcalc
The two methods are statistically comparable
Fcalc = [pic]
Fcalc = 676
Ftable = 9.28
Fcalc > Ftable
The variances of the two methods are statistically different

The average percent of iron present in the unknown sample was 10.95% Fe with a standard deviation of ± 0.5% Fe. When statistically compared to an alternative method of determining percent iron in the same unknown sample using Beer’s