Consider the unbalanced equation for the oxidation of aluminum. _ Al plus _ cap o sub 2 rightarrow _ Al sub 2 cap o sub 3 Which sequence of coefficients should be placed in the blanks to balance this equation?

Each Al₂O₃ unit contains 2 aluminum atoms and 3 oxygen atoms. Put 2 in front of Al₂O₃ to make 4 aluminum atoms and 6 oxygen atoms on the right; then use 4Al and 3O₂ on the left to match. The balanced equation is 4Al + 3O₂ → 2Al₂O₃, so the correct choice is 4, 3, 2.

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