Question

18 g of steam reacted with iron to form $Fe_3O_4$, how much iron will be consumed.

• A. 21 gm
• B. 42 gm
• C. 84 gm
• D. 10.5 gm

Answer 1

The Correct Option is B

This is a stoichiometry problem involving the reaction between iron ($Fe$) and steam ($H_2O$).
1. Write the balanced chemical equation:
$3Fe + 4H_2O(\text{steam}) \rightarrow Fe_3O_4 + 4H_2$

2. Calculate moles of given reactant:
Mass of steam ($H_2O$) = 18 g.
Molar mass of $H_2O = 18 \text{ g/mol}$.
Moles of steam, $n_{H_2O} = \frac{18}{18} = 1 \text{ mole}$.

3. Use stoichiometry to find moles of Iron:
From the balanced equation, 4 moles of $H_2O$ react with 3 moles of $Fe$.
So, 1 mole of $H_2O$ will react with $\frac{3}{4}$ moles of $Fe$.
$n_{Fe} = 0.75 \text{ moles}$.

4. Convert moles of Iron to mass:
Atomic mass of $Fe = 56 \text{ g/mol}$.
Mass of $Fe = 0.75 \times 56 = 42 \text{ gm}$.

Thus, 42 gm of iron will be consumed. Option (2) is correct.