Difference of Sodium Tungstate and Sodium Molybdate

The difference between sodium tungstate and sodium molybdate is reflecting in their physical and chemical properties and application, they are two different substances, but because of tungsten and molybdenum belong to the same family of ⅥB, so that there are some similarities in physical and chemical properties , but a lot of differences exist.

Difference of Physical Property

Name Sodium Tungstate Sodium Molybdate
Chemical Formula Na2WO4 Na2Mo4
Molar Mass 293.82 g·mol−1 205.92 (Anhydrous) g·mol−1
241.95 (Dihydrate) g·mol−1
Density 4.179 g/cm3
3.23 g/cm3(Dihydrate)
3.78 g/cm3, solid
Appearance White Diamond Crystal White Powder
Melting Point 698°C 687 °C
CAS Number 13472-45-2
10213-10-2(Sodium Tungstate Dihydrate)
7631-95-0
10102-40-6 (Sodium Molybdate Dihydrate)
Solubility (Water) 74.2 g/100 mL 84 g/100 ml (100 °C)
Solubility (Other Solvents) Slightly Soluble in Ammonia, Insoluble in Ethanol Insoluble in Acetone

 

Difference of Chemical Property

When sodium tungstate meets strong acid, it will generate tungstic acid precipitation:
Na2WO4+2HCl—Boiling→H2WO4↓(Yellow)+2NaCl
Na2WO4+2HCl+H2O→H2WO4•H2O↓(White)+2NaCl
Sulfur atom will substitute the oxygen atom in tungstate radical one by one when hydrogen sulfide inlets into sodium tungstate solution, and finally generate tetrathiocarbonate sodium tungstate.

Sodium molybdate will react with acid to produce molybdic acid precipitation:
Na2MoO4+2HCl→H2MoO4↓+2NaCl

sodium tungstate photosodium molybdate picture

Difference of Application

Sodium tungstate is the raw material of manufacturing metal tungsten, tungstic acid and tungstate salts; also used as a mordant, catalyst and pigments, as well as fabric fire retardant and chemical analysis reagents ect.; also, it is widely used in industries of petroleum, aerospace and defense.

Sodium molybdate is mainly used as metal corrosion inhibitor, descaling agent, bleaching agent and protective agent of skin and hair; alkaloids, dyes and analytical reagent for pharmaceutical industry.

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More info>>

1.Tungsten Trioxide

2.Tungsten Oxide