The formation of alumina, Al2O3, can be illustrated by the reaction below: 

4 Al (s) + 3 O2 (g) →  2 Al2O3 (s). 

At 750 K it takes 267 seconds for the initial concentration of Al2O3 to increase from 6.18 x 10-5 M to 5.11 x 10-4 M. What is the average rate of Al? 

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