Question

select the correct answer.
iron reacts with atmospheric oxygen to form iron oxide or ferric oxide. look at the chemical equation for this reaction:
fe + o₂ → fe₂o₃
this equation is unbalanced. which of the following is the correct balanced equation for this reaction?
a. 4fe + 3o₂ → 2fe₂o₃
b. 3fe + 4o₂ → 2fe₂o₃
c. 2fe + 4o₂ → 3fe₂o₃
d. 3fe + 3o₂ → 4fe₂o₃
e. 4fe + 4o₂ → 3fe₂o₃

Explanation:

Step1: Count Fe atoms per side

Unbalanced: Reactants: $1$ Fe; Products: $2$ Fe

Step2: Balance Fe atoms

Assign coefficient 2 to Fe: $2\text{Fe} + \text{O}_2
ightarrow \text{Fe}_2\text{O}_3$
Now Fe: Reactants $2$, Products $2$

Step3: Count O atoms per side

Reactants: $2$ O; Products: $3$ O

Step4: Balance O atoms

Use least common multiple of 2 and 3 (6). Assign coefficient 3 to $\text{O}_2$, coefficient 2 to $\text{Fe}_2\text{O}_3$:
$2\text{Fe} + 3\text{O}_2
ightarrow 2\text{Fe}_2\text{O}_3$
Now O: Reactants $6$, Products $6$

Step5: Rebalance Fe atoms

Products have $4$ Fe, assign coefficient 4 to Fe:
$4\text{Fe} + 3\text{O}_2
ightarrow 2\text{Fe}_2\text{O}_3$
Now Fe: Reactants $4$, Products $4$

Answer:

A. $4\text{Fe} + 3\text{O}_2
ightarrow 2\text{Fe}_2\text{O}_3$