In the reaction $4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \rightarrow X + Y + 8CO_2$,identify $X$ and $Y$.

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

Which of the following processes is $NOT$ involved in the extraction of metal from cassiterite $(SnO_2)$ ore?

Which metals are used in the currency of the $UK$?

Among the reactions $(a) - (d)$,the reaction$(s)$ that does/do not occur in the blast furnace during the extraction of iron is/are:
$(a)$ $CaO + SiO_2 \rightarrow CaSiO_3$
$(b)$ $3 Fe_2O_3 + CO \rightarrow 2 Fe_3O_4 + CO_2$
$(c)$ $FeO + SiO_2 \rightarrow FeSiO_3$
$(d)$ $FeO \rightarrow Fe + \frac{1}{2} O_2$

Which of the following changes involve more than two metallurgical processes?