Question

Calculate the percentage of pure aluminium in 10 kg of aluminium oxide $\left[A{l}_2{O}_3\right]$ of 90 % purity.
[Al=27, O=16]

• A. 90 %
• B. 23.94 %
• C. 47.64 %
• D. 94.58 %

Answer 1

Answer: (C)

47.64 %

As sample is 90 % pure only so, mass of $A{l}_2{O}_3=9kg$
Mass of Al $=2\times 27\times 9/102=4.76kg$
% of Al in sample $4.76\times 10/100=47.6$ %