Question

Aluminum is a highly reactive metal that oxidizes when exposed to air. Which of these would be a good first step in balancing this reaction? Al + O2 → Al2O3 A) Put a coefficient of 3 on Al B) Put a coefficient of 3 on O2 C) Put a coefficient of 2 on O2 D) Put a coefficient of 3 on Al2O3

Answer 1

The answer is B. because when u add 3 on O2 and multiplied together makes 6

Answer 2

Answer: B) Put a coefficient of 3 on $O_2$

Explanation: According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

The balancing starts with the maximum number of atoms and thus first oxygen needs to get balanced by putting a coefficient of 3 on reactant side.

The balanced chemical equation will be:

$4Al+3O_2\rightarrow 2Al_2O_3$