How to calculate the molar proportions of the oxides from the XRF analyses?
Dear Almachius Tryphone Muatsingwa ,
please google for tutorials on that subject;
you will find for example:
elements composition to oxides:
https://www.youtube.com/watch?v=suGpwOF7gPI
oxides composition to elements:
https://www.youtube.com/watch?v=nVQRzbyy7eA
Good luck and
best regards
G.M.
Dear Almachius Tryphone Muatsingwa
To obtain the molar proportion of oxides (from any type of chemical analyses, including XRF but not limited to it), you can follow this procedure:
1) Divide the measured mass percent (or wt%) by the respective oxide molar mass. Here you will obtain the molar amount for each oxide.
2) Sum the result from step 1 (molar amount) of all oxides.
3) Divide each molar amount (step 1) by the sum values obtained in step 2.
An example from a fictitious analysis:
SiO2 = 70% (g/g)
Al2O3 = 18% (g/g)
Fe2O3 = 1% (g/g)
CaO = 2% (g/g)
Na2O = 4% (g/g)
K2O = 5% (g/g)
Molar masses:
SiO2 = 60.08 g/mol
Al2O3 = 101.96 g/mol
Fe2O3 = 159.69 g/mol
CaO = 56.08 g/mol
Na2O = 61.98 g/mol
K2O = 94.2 g/mol
1) molar amounts in the sample:
SiO2 = 70/60.08 = 1.17 mol/g
Al2O3 = 18/101.96 = 0.18 mol/g
Fe2O3 = 1/159.69 = 0.01 mol/g
CaO = 2/56.08 = 0.04 mol/g
Na2O = 4/61.98 = 0.06 mol/g
K2O = 5/94.2 = 0.05 mol/g
2) Sum of molar amounts = 1.5 mol/g
3) Molar fraction (or proportion):
SiO2 = 1.17/1.5 = 0.78
Al2O3 = 0.18/1.5 = 0.12
Fe2O3 = 0.01/1.5 = 0.004
CaO = 0.04/1.5 = 0.02
Na2O = 0.06/1.5 = 0.04
K2O = 0.05/1.5 = 0.04
Kind regards,
Fernando
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