Answer:
Coefficients = { 4, 3, 2 }
Step-by-step explanation:
The previous answer is correct, but I want to show you how to balance this chemical reaction. First take a look at the number of each element present in the reactant and product side -
Reactant | Product
Aluminum = 1 Aluminum = 2
Oxygen = 2 Oxygen = 3
As you can see, if you were to double the aluminum on the reactant side, the reactant and product side with respect to aluminum would be balanced. 2 and 3 share a least common multiple of 6, so if we were to triple the amount of oxygen on the reactant side and double the amount of oxygen on the product side - either side would be balanced!
Now there is one default in this. The number of aluminum and oxygen on the product side are present as the same compound. Let us say we were to still triple the amount of oxygen on the reactant side and double the amount of oxygen on the product side. That would satisfy the oxygens. The chemical equation would then be as such -
Al + 3O2 -----> 2Al2O3
Now let us balance the number of aluminums on either side. There is 1 aluminum on the reactant side, with respect to 4 aluminums on the product side. The coefficient of aluminum on the reactant side should thus be four -
4Al + 3O2 -----> 2Al2O3
Coefficients = { 4, 3, 2 }