Question

Given the unbalanced equation: __Al(s) + __O2(g) → __Al2O3(s), when this equation is correctly balanced using the smallest whole numbers, what is the coefficient of O2(g)?

A) 6
B) 2
C) 3
D) 4

Answer 1

The coefficient of O2(g) when the equation 4Al(s) + 3O2(g) → 2Al2O3(s) is balanced is 3.

Step-by-step explanation:

To balance the aluminum and oxygen in the reaction Al(s) + O2(g) → Al2O3(s), we need to ensure that the number of aluminum and oxygen atoms are equal on both sides of the equation. Starting with aluminum, we can see that there are 2 aluminum atoms in the product Al2O3, so we need 2 aluminum atoms on the reactant side as well. We place the coefficient 4 in front of Al to get 4Al. For the oxygen, there are 3 oxygen atoms in the product Al2O3. To balance the oxygen atoms, we need a total of 6 oxygen atoms on the reactant side (since 2 Al2O3 molecules will give us 6 oxygen atoms). Thus, we place the coefficient 3 in front of O2 because it would provide 6 oxygen atoms. So our balanced equation now reads 4Al(s) + 3O2(g) → 2Al2O3(s), and the correct coefficient of O2(g) is 3.