The mass of carbon anode consumed (giving only carbon dioxide) in the production of 270 kg of aluminium metal from bauxite by the Hall process is (Atomic mass : Al = 27)

$\begin{array}{l}2{\mathrm{Al}}_2{\mathrm{O}}_3+3\mathrm{C}\stackrel{ }{\to }\mathrm{Al}+3{\mathrm{CO}}_2\\ \mathrm{Gram}\mathrm{equivalent}\mathrm{of}{\mathrm{Al}}_2{\mathrm{O}}_3=\mathrm{Gram}\mathrm{equivalent}\mathrm{of}\mathrm{C}.\\ \mathrm{Now}\mathrm{equivalent}\mathrm{weight}\mathrm{of}\mathrm{Al}=\frac{27}{3}=9\\ \mathrm{Equivalent}\mathrm{weight}\mathrm{of}\mathrm{C}=\frac{12}{4}=3\left(\stackrel{0}{\mathrm{C}}\to \stackrel{+4}{\mathrm{C}}{\mathrm{O}}_2\right)\\ \mathrm{No}.\mathrm{of}\mathrm{gram}\mathrm{equivalent}\mathrm{of}\mathrm{Al}=\frac{\mathrm{wt}.}{\mathrm{E}}=\frac{270\times {10}^3}{9}=30\times {10}^3\\ \mathrm{Hence},\\ \mathrm{No}.\mathrm{of}\mathrm{gram}\mathrm{equivalent}\mathrm{of}\mathrm{C}=30\times {10}^3\\ \mathrm{Again},\\ \mathrm{No}.\mathrm{of}\mathrm{gram}\mathrm{equivalent}\mathrm{of}\mathrm{C}\\ =\frac{\mathrm{mass}\mathrm{in}\mathrm{gram}}{\mathrm{gram}\mathrm{equivalent}\mathrm{weight}}\\ \Rightarrow 30\times {10}^3=\frac{\mathrm{mass}}{3}\\ \Rightarrow \mathrm{mass}=90\times {10}^3\mathrm{g}=90\mathrm{kg}\end{array}$