% Mgo Determination

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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)| 73.0| 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...
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