Question

In an iron powder-based oxygen scavenger, one gram of iron can react with ____ oxygen at standard temperature and pressure.

• A. 0.0136 mol
• B. 0.3030 mol
• C. 1.0306 mol
• D. 0.0007 mol

Hint:

To solve this stoichiometry problem quickly, remember that 1 gram of iron is about 0.018 moles, which reacts with $3/4$ that amount of oxygen, yielding approximately 0.0135 moles of $\text{O}_2$.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Oxygen scavengers are active packaging technologies used to remove residual oxygen from sealed food packages, preventing oxidative rancidity and aerobic microbial growth.
The most common oxygen scavengers utilize the oxidation of iron powder in the presence of moisture.
Key Formula or Approach:
The oxidation of iron ($\text{Fe}$) in the presence of water and oxygen can be represented by the following chemical equation:
\[ 4\text{Fe} + 3\text{O}_2 + 6\text{H}_2\text{O} \rightarrow 4\text{Fe(OH)}_3 \] From the stoichiometry of this reaction:
\[ 4\text{ moles of Fe} \text{ react with } 3\text{ moles of O}_2 \]

Step 2: Detailed Explanation:
Let us calculate the moles of oxygen ($\text{O}_2$) that react with 1 gram of iron ($\text{Fe}$):
1. Find the moles of iron in 1 gram:
The atomic mass of iron ($\text{Fe}$) is approximately $55.85\text{ g/mol}$.
\[ \text{Moles of Fe} = \frac{1\text{ g}}{55.85\text{ g/mol}} \approx 0.0179\text{ mol} \]
2. Use the stoichiometric ratio from the balanced chemical equation:
The ratio of $\text{O}_2$ to $\text{Fe}$ is $\frac{3}{4} = 0.75$.
\[ \text{Moles of O}_2 = 0.0179\text{ mol of Fe} \times 0.75 \approx 0.0134\text{ mol} \]
Looking at the options, the value $0.0136\text{ mol}$ is the closest match to our calculated value of $0.0134\text{ mol}$, accounting for minor variations in atomic mass values or hydration state definitions.

Step 3: Final Answer
The correct option is (A).