Determination of %MgO
using a Compleximetric Titration
The procedure for this experiment is taken from the laboratory manual referenced below. There were no significant deviations from that procedure.
Mass of Na2EDTA*2H2O _0.9864 g
Molar Mass of Na2EDTA*2H2O 372.25 g/mol
Estimated Morality of EDTA solution ____0.0088M_________________
Standardization of EDTA Solution
Concentration of Zn2+ 0.0112M
| Trial #1 | Trial #2 | Trial #3 |
Final Buret Reading | 10.50 ml | 9.20 ml | 26.50 ml |
Initial Buret reading | 3.00 ml | 2.00 ml | 18.50 ml |
Volume used, EDTA | 7.50 ml | 7.20 ml | 8.00 ml |
...view middle of the document...
12*10-4 mol EDTA/0.0075L EDTA = 0.0149M EDTA
Determination of %MgO of Unknown
Using data from Sample #1
38.80ml EDTA – 0.00ml Blank = 38.80ml EDTA = 0.0388L EDTA
Moles of Mg2+ in a sample using average M EDTA and volume of EDTA:
(0.0148M EDTA) *(0.0388L EDTA) = 5.7424*10-4 mol EDTA = 5.7424*10-4 mol Mg2+
%MgO= (5.7424*10-4 mol Mg2+ )*(40.305 g/mol MgO)*(100)/0.2100g sample mass = 11.021%
The average concentration of the EDTA solution was 0.0148M.
The average % MgO in unknown #1W was 11.5580%.
Measurements of blank DI water did not show a presence of metal ions.
The most important source of error came from the buret readings. Adding EDTA solution too rapidly, offsets the correct amount of EDTA solution used in the titration and effects the deviations in %MgO calculations.
The expected molarity of EDTA solution based on the molar mass of the sample was 0.0088M. However, the value obtained from standardization of EDTA using Zn2+ was 0.0148M, about 5.6% deviation that also affects the results of %MgO determination leaving 94.4% confidence in...