Answered

Select the correct answer.

Iron reacts with atmospheric oxygen to form iron oxide or ferric oxide. Look at the chemical equation for this reaction:

[tex]\[ Fe + O_2 \rightarrow Fe_2O_3 \][/tex]

This equation is unbalanced. Which of the following is the correct balanced equation for this reaction?

A. [tex]\( 4 Fe + 3 O_2 \rightarrow 2 Fe_2O_3 \)[/tex]
B. [tex]\( 3 Fe + 4 O_2 \rightarrow 2 Fe_2O_3 \)[/tex]
C. [tex]\( 2 Fe + 4 O_2 \rightarrow 3 Fe_2O_3 \)[/tex]
D. [tex]\( 3 Fe + 3 O_2 \rightarrow 4 Fe_2O_3 \)[/tex]
E. [tex]\( 4 Fe + 4 O_2 \rightarrow 3 Fe_2O_3 \)[/tex]



Answer :

To balance the chemical equation for the reaction between iron (Fe) and oxygen (O₂) to form ferric oxide (Fe₂O₃), we need to ensure that there are equal numbers of each type of atom on both sides of the equation. Let’s balance this step-by-step.

The unbalanced equation is:
[tex]\[ \text{Fe} + \text{O}_2 \rightarrow \text{Fe}_2\text{O}_3 \][/tex]

1. Balance the iron (Fe) atoms:
- On the right side of the equation, Fe₂O₃ contains 2 iron atoms (Fe).
- Therefore, on the left side, we need 2 Fe atoms to balance the iron atoms.
[tex]\[ 2 \text{Fe} + \text{O}_2 \rightarrow \text{Fe}_2\text{O}_3 \][/tex]

2. Balance the oxygen (O) atoms:
- On the right side, Fe₂O₃ contains 3 oxygen atoms (O).
- On the left side, O₂ is diatomic and contains 2 oxygen atoms per molecule. We need to find how many O₂ molecules will provide 3 oxygen atoms.
- If we multiply O₂ by 3/2 or 1.5, we get:
[tex]\[ \frac{3}{2} \text{O}_2 = 3 \text{ oxygen atoms} \][/tex]
- To avoid fractions in the balanced equation, multiply all coefficients by 2 to make whole numbers.
[tex]\[ 4 \text{Fe} + 3 \text{O}_2 \rightarrow 2 \text{Fe}_2\text{O}_3 \][/tex]

Now, the equation is balanced with:
- 4 iron atoms (Fe) on both sides.
- 6 oxygen atoms (O) on both sides (3 O₂ molecules on the left yield 6 O atoms, and 2 Fe₂O₃ molecules on the right have 2×3 = 6 O atoms).

The correct balanced equation for the reaction is:
[tex]\[ 4 \text{Fe} + 3 \text{O}_2 \rightarrow 2 \text{Fe}_2\text{O}_3 \][/tex]

Therefore, the correct answer is:
A. [tex]\( 4 \text{Fe} + 3 \text{O}_2 \rightarrow 2 \text{Fe}_2\text{O}_3 \)[/tex]