Question

The given reaction is balanced so that its coefficient is the lowest whole-number. Find the coefficient of ${O_2}$.
$Al(s) + {O_2}(g) \to A{l_2}{O_3}(s)$
(A) 6
(B) 4
(C) 2
(D) 3
(E) 1

Answer 1

Hint In order to balance the given chemical equation, we must first know what a balanced equation is. We should also have an idea about how to balance the chemical equation. When the number of atoms present in both the reaction and product side in a given chemical equation is equal. This is called the balanced chemical equation.

Complete step by step solution:
First let us understand what a chemical equation is. When a chemical reaction is represented in the chemical symbol, then it is called a chemical equation. A chemical equation will be having a reactant, product and an arrow to represent the direction. When the number of atoms present in both the reaction and product side in a given chemical equation is equal. This is called the balanced chemical equation. Now let us move onto the given question.
$Al(s) + {O_2}(g) \to A{l_2}{O_3}(s)$
The above given reaction is an unbalanced reaction. We have to balance the reaction by making the number of each element present in the left and right side equal.
The oxygen on the right side is three, in order to make the oxygen equal we have to multiply by on the left side. Therefore, on both the sides the oxygen present is three.
The Aluminium on the right side is two and the number of aluminium present on the left side is one. In order to make both sides equal, we have to multiply the aluminium on the left side by 2.
$2Al(s) + \frac{3}{2}{O_2}(g) \to A{l_2}{O_3}(s)$
In order to make the above given equation in the whole number, we have to multiply by 2. We get the balanced equation as
$4Al(s) + 3{O_2}(g) \to 2A{l_2}{O_3}(s)$
Therefore, the lowest whole number coefficient of the oxygen atom is found to be 3.

Hence the correct answer is option (D) 3.

Note: When we are writing a chemical equation, we should never forget to balance the equation because when the chemical equation is unbalanced, then the equation is incorrect or incomplete. Therefore, always remember to balance the chemical equation.