The value of $\mathrm{n}$ in the molecular formula ${\mathrm{Be}}_{\mathrm{n}}{\mathrm{Al}}_2{\mathrm{Si}}_6{\mathrm{O}}_{18}$ is

The oxidation number of $\mathrm{Mn}$ in the product of alkaline oxidative fusion of ${\mathrm{MnO}}_2$ is. 

How many grams of potassium dichromate are required to oxidise $20.0 \mathrm{g}$ of ${\mathrm{Fe}}^{2+}$ in ${\mathrm{FeSO}}_4$ to ${\mathrm{Fe}}^{3+}$ if the reaction is carried out in an acidic medium ? (Molar mass of ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ and ${\mathrm{FeSO}}_4$ are $294$ and $152$ respectively)

Round off your answer to the nearest integer.