I have bought a compound(powder) called "ammonium niobate (V) oxalate hydrate" from Sigma Aldrich. The molecular formula of this compound is NH4[NbO(C2O4)2].xH2O or NH4[NbO(H2O)2(C2O4)2].xH2O written differently in some articles.

(I am still confused that these two formulas might be for different compounds)

But the nominal molecular weight (302.98g/mol) provided by the supplier is anhydrous base.

I should weight an exact molar ratio of Nb cation to other cations in aqueous solution based on the molecular weight of starting materials. However, because of the undetermined degree of hydration (xH2O), it is not possible.

Will this compound be transformed into an anhydrous form by drying at 120 C overnight?

I could not find any literature clearly confirming it.

If it is the case, is the molecular formula of anhydrous form NH4[NbO(C2O4)2]?

I will be grateful if someone answer my question. Thank you.