Ervin Toh Wei Yao's answer to Rosie's Secondary 4 E Maths Singapore question.

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Ervin Toh Wei Yao
Ervin Toh Wei Yao's answer
9 answers (Tutor Details)
1st
You must find the percentage by mass of the aluminum oxide within the compound X, which gives 21.1%.

Thereafter, you must find the percentage by mass of the aluminum element within the aluminum oxide, via calculation of molar mass, which gives 52.94%.

Finally, for the % of the aluminum element within the compound X, taking 52.94% of the 21.1% results in 11.17%, which rounds up to 11.2%.