Question

a hand warmer packet contains iron powder (fe) that reacts with oxygen in the air to produce heat. the reaction forms iron(iii) oxide, fe₂o₃. calculate the molar mass of fe₂o₃. compare the molar mass of fe₂o₃ to the molar mass of o₂. which one is heavier? explain. ©science korner 2025

Explanation:

First Sub - Question: Calculate the molar mass of $\ce{Fe_{2}O_{3}}$

Step 1: Recall atomic masses

The atomic mass of $\ce{Fe}$ (iron) is approximately $55.85\space g/mol$ and the atomic mass of $\ce{O}$ (oxygen) is approximately $16.00\space g/mol$.

Step 2: Calculate molar mass of $\ce{Fe_{2}O_{3}}$

For $\ce{Fe_{2}O_{3}}$, we have 2 atoms of $\ce{Fe}$ and 3 atoms of $\ce{O}$. The formula for molar mass ($M$) is $M = 2\times M_{Fe}+3\times M_{O}$.
Substitute the values: $M = 2\times55.85 + 3\times16.00$.
First, calculate $2\times55.85=111.7$ and $3\times16.00 = 48.00$.
Then, add them together: $111.7+48.00 = 159.7\space g/mol$.

Step 1: Calculate molar mass of $\ce{O_{2}}$

The atomic mass of $\ce{O}$ is $16.00\space g/mol$. For $\ce{O_{2}}$, the molar mass $M_{O_{2}}=2\times16.00 = 32.00\space g/mol$.

Step 2: Compare molar masses

We found that the molar mass of $\ce{Fe_{2}O_{3}}$ is approximately $159.7\space g/mol$ and the molar mass of $\ce{O_{2}}$ is $32.00\space g/mol$. Since $159.7>32.00$, $\ce{Fe_{2}O_{3}}$ has a greater molar mass, meaning it is heavier on a molar basis.

Answer:

The molar mass of $\ce{Fe_{2}O_{3}}$ is approximately $159.7\space g/mol$.

Second Sub - Question: Compare the molar mass of $\ce{Fe_{2}O_{3}}$ to the molar mass of $\ce{O_{2}}$. Which one is heavier? Explain.