Spiegeleisen is an alloy of

Identify the products of the reaction: $4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \rightarrow ?$

Read the following statements :
$(I)$ $Al$ has greater affinity than that of $Cr$ for oxygen
$(II)$ $Al$ can be used for reduction of $Fe_2O_3$
$(III)$ Carbon is used for reduction of $PbO$
$(IV)$ $SnO_2$ can be reduced by carbon
Choose the correct set of statement$(s)$:

The molar mass of the water-insoluble product formed from the fusion of chromite ore $(FeCr_2O_4)$ with $Na_2CO_3$ in the presence of $O_2$ is $..........$ $g \ mol^{-1}$.

Percentage of silver in German silver is (in $\%$)

How is cement clinker obtained?