The mass of carbon anode consumed (giving only carbondioxide) in...

The mass of carbon anode consumed (giving only carbondioxide) in the production of 270 g of aluminium metal from bauxite by the Hall process is (Atomic mass

\mathrm{Al}=27

)

Options

A180 g
B270 g
C540 g
D90 g

Correct answer

D. 90 g

Step-by-step solution

In Hall and Heroult process

\begin{aligned} 2 \mathrm{Al}_2 \mathrm{O}_3 & \longrightarrow 4 \mathrm{Al}+3 \mathrm{O}_2 \\ 4 \mathrm{C}+3 \mathrm{O}_2 & \longrightarrow 2 \mathrm{CO}_2+2 \mathrm{CO} \uparrow \\ 2 \mathrm{Al}_2 \mathrm{O}_3+4 \mathrm{C} & \longrightarrow 4 \mathrm{Al}+2 \mathrm{CO}_2+2 \mathrm{CO}\end{aligned}

Only for removal of

\mathrm{CO}_2

, following equation is possible

2 \mathrm{Al}_2 \mathrm{O}_3+\underset{3 \times 12=36}{3 \mathrm{C}} \longrightarrow \underset{4 \times 27=108}{4 \mathrm{Al}}+3 \mathrm{CO}_2 \because

For 108 g of

\mathrm{Al}, 36 \mathrm{~g}

of C is required in above reaction.

\therefore For

270 g of Al require amount of C =

\frac{36}{108}

\times 270=90

\mathrm{~g}

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