Question

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: $Al = 27$):

• A. $90\, kg$
• B. $540\,kg$
• C. $270\, kg$
• D. $180\, kg$

Answer 1

Answer: (A)

$2Al_2O_3 + 3C \to Al + 3CO_2$
Gram equivalent of $Al_2O_3 \equiv$ Gram equivalent of $C$.
Now equivalent weight of $Al = \frac{27}{3} = 9$
Equivalent weight of $C = \frac{12}{4} = 3 (\overset{0}{C} \to \overset{+4}{CO_2})$
No. of gram equivalent of $Al = \frac{270 \times 10^3}{9} = 30 \times 10^3$
Hence,
No. of gram equivalent of $C= 30 \times 10^3$
Again,
No. of gram equivalent of $C$
$= \frac{\text{mass in gram}}{\text{gram equivalent weight}}$
$\Rightarrow 30 \times 10^3 = \frac{mass}{3}$
$\Rightarrow $ mass $ = 90 \times 10^3 \,g = 90 \,kg$