Which of the following represents the correctly balanced chemical equation for the reaction of aluminum with oxygen to form aluminum oxide?

• A. 2 Al + 3 O2 -> Al2O3
• B. 2 Al + O2 -> Al2O3
• C. 4 Al + 3 O2 -> 2 Al2O3
• D. 4 Al + O2 -> 2 Al2O3

Answer: (C)

Balancing a chemical equation means making sure every element has the same number of atoms on both sides. Aluminum oxide has the formula Al2O3, so each unit contains 2 aluminum atoms and 3 oxygen atoms. Oxygen comes from O2, so the oxygen side must be supplied by whole O2 molecules.

If you aim for 2 units of aluminum oxide on the product side, you need 4 aluminum atoms in total and 6 oxygen atoms (because 2 × Al2O3 has 4 Al and 2 × 3 O = 6 O). The 6 oxygen atoms come from 3 molecules of O2 (since each O2 has 2 oxygen atoms, 3 × 2 = 6). That means the left side must have 4 Al atoms and 3 O2 molecules: 4 Al + 3 O2.

Thus the balanced equation is 4 Al + 3 O2 -> 2 Al2O3. The other attempts don’t balance both elements: they either don’t provide enough oxygen atoms or don’t match the aluminum count, so they’re not chemically balanced.