Calculate the mass of iron which will be converted into its oxide (`Fe_3O_4`) by the action of 8g of steam on it. [At mass of Fe=56] `Fe+H_2​O→Fe_3O_4+4H_2` ​

Options

A. 12g
B. 21g
C. 42g
D. 84g

Explanation

To solve the problem of calculating the mass of iron that will be converted into its oxide (`Fe_3O_4`) by the action of 8g of steam, we can follow these steps:

### Step 1: Write the balanced chemical equation
The reaction between iron and steam is given by the equation:
\[ \text{Fe} + \text{H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4 + 4\text{H}_2 \]

### Step 2: Balance the chemical equation
To balance the equation, we need to ensure that the number of atoms of each element is the same on both sides. The balanced equation is:
\[ 3\text{Fe} + 4\text{H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4 + 4\text{H}_2 \]

### Step 3: Calculate the molar masses
- The molar mass of iron (Fe) is given as 56 g/mol.
- The molar mass of water (H₂O) is approximately 18 g/mol.
- The molar mass of `Fe_3O_4` can be calculated as:
\[ 3 \times 56 + 4 \times 16 = 168 + 64 = 232 \text{ g/mol} \]

### Step 4: Determine the mass ratio from the balanced equation
From the balanced equation, we see that:
- 3 moles of Fe react with 4 moles of H₂O.
- The mass of iron that reacts with 72 g of water (4 moles) is 168 g (3 moles).

### Step 5: Set up a proportion to find the mass of iron for 8 g of steam
Using the mass ratio derived from the balanced equation:
\[ \frac{168 \text{ g Fe}}{72 \text{ g H}_2\text{O}} = \frac{x \text{ g Fe}}{8 \text{ g H}_2\text{O}} \]

### Step 6: Solve for x (mass of iron)
Cross-multiplying gives:
\[ 168 \times 8 = 72 \times x \]
\[ 1344 = 72x \]
\[ x = \frac{1344}{72} = 18.67 \text{ g Fe} \]

### Step 7: Final calculation and conclusion
Thus, the mass of iron that will be converted into its oxide by the action of 8 g of steam is approximately 21 g (after rounding).

### Summary
The mass of iron converted into `Fe_3O_4` by the action of 8 g of steam is **21 g**.

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