The molar mass of the water insoluble product formed from the fusion of chromite ore ( FeCr_2 O_4) with Na_2 CO_3 in presence of O_2 is ____ g mol^-1.

The molar mass of the water insoluble product formed from the fusion of chromite ore $\displaystyle \left(\mathrm{FeCr}_2 \mathrm{O}_4\right)$ with $\displaystyle \mathrm{Na}_2 \mathrm{CO}_3$ in presence of $\displaystyle \mathrm{O}_2$ is $\displaystyle \_\_\_\_$ $\displaystyle \mathrm{g} \mathrm{mol}^{-1}$.