% Mgo Determination

Vu Ngo % MgO Determination September 10, 2012 Procedure: Reference to lab manual Data: Mass of Na2EDTA†¢2H2O, g| . 9289| Standardization of EDTA Solution | Trial 1| Trial 2| Final buret reading, EDTA (mL)| 18. 5| 36. 7| Initial buret reading, EDTA(mL)| 0. 5| 18. 5| Determination of % MgO of Unknown Unknown Number | 4J| | Sample 1| Sample 2| Sample 3| Mass of sample (g)| 0. 2135| 0. 2132| 0. 2139| Final buret reading, EDTA (mL)| 73. 5| 74. 2| 74. 2| Initial buret reading, EDTA(mL)| 0. 5| 0| 0| Measurement of water blank Final buret reading, EDTA(mL)| 14. 5| Initial buret reading, EDTA(mL)| 14. 2| Sample Calculation:Given: Molar mass of Na2EDTA*2H2O, g/mol| 372. 25| Expected M of EDTA solution, mol/L (M)| 0. 01| Concentration of Zn2+, (M)| 0. 0125| 10mL*1L1000mL= 0. 01L C1V1=C2V2 .0125M. 010L)=C2(. 018L) C2=. 0125M*. 0100L. 0180L=. 00694M .00694M+. 0687M2=. 00691M C2=. 00691M. 073=5. 04*10-4mol %MgO=5. 04*10-4mol40. 05. 2135g*100=9. 51% Results: Standardization of EDTA Solution | Trial 1| Trial 2| Volume used, EDTA(mL)| 18. 0| 18. 2| Molarity of EDTA solution, (M)| 0. 00694| 0. 00687| Average Molarity of EDTA solution, (M)| 0. 00691| Determination of % MgO of Unknown | Sample 1| Sample 2| Sample 3| Volume used, EDTA (mL)| 73. | 74. 2| 74. 2| Mole of Mg2+in sample| 5. 04E-04| 5. 12E-04| 5. 12E-04| % of MgO in sample, %| 9. 52| 9. 69| 9. 66| Average % of MgO in sample, %| 9. 62| Error Analysis: The measurement of the sample in gram, have +/- . 0001g error. The measurement using the the buret have a +/- . 1mL error. These types of measurement error are based on the sensitivity of the instrument, during the measurement. These errors could cause the result to deviate from the actual answer. During the experiment, using titration to find the end point. Because of the end point was unknown, a single drop could determine its end point.There might be an extra drop that caused the data to vary as both parts of the experiment have determined. The first trial of both th e experiment, the number is different, because of the unsure number of drops. Using the result from the first trial, the result of the second trial was more accurate. As proven from the experiment of determination of percent of MgO of the unknown. The sample 2 and sample 3 testing results in similarity that differ from the sample one. The sample used 73. 0 ml of the EDTA solution, while both samples 2 and 3 used 74. 2 ml of EDTA solution.This will cause a tip in the result toward a lower number used to find the end point. This error is not a major factor since it is only of my 1. 2 ml of the actual result. The percent of all three result of MgO is different under 1 percent different. Thus, a very reasonable result in all three of the experiment. Discussion: This experiment is to help us understand the reaction between an anion and the metal cation. It demonstrated the Lewis base understanding of ethylenediaminetetraacetic acid (EDTA). The goal was achieved through titration of the s ample in multiple trials in order to find its endpoint.The end point was found when the pink coloration, due to EBT was added, turn into a blue/ violet color. This signified its endpoint of the sample. The result is good quality, because of the deviation from the first trial and last trial that was done on the same sample. The result is off by . 2ml in the standardization of EDTA solution. In the second part of the determination of % MgO of the unknown; the first, second, and third sample the percentage displaces is well under 1% difference. The result is worth 99% confident that the result is good quality, because of the consistency of the data.