1. When iron reacts with oxygen, it forms iron oxide, or rust.

4 Fe + 3 O2 2 Fe2O3


If 112 g of iron (Fe) combines with 24 g of oxygen (O2), how much iron oxide is formed?

Verified Answer :

136g of iron oxide will be produced

Answer: The mass of iron (III) oxide produced is 59.9 grams.

Explanation:

To calculate the number of moles, we use the equation:

\(\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}\)      .....(1)

  • For iron:

Given mass of iron = 112 g

Molar mass of iron = 55.84 g/mol

Putting values in equation 1, we get:

\(\text{Moles of iron}=\frac{112g}{55.84g/mol}=2mol\)

  • For oxygen gas:

Given mass of oxygen gas = 24 g

Molar mass of oxygen gas = 32 g/mol

Putting values in equation 1, we get:

\(\text{Moles of oxygen gas}=\frac{24g}{32g/mol}=0.75mol\)

The given chemical equation follows:

\(4Fe+3O_2\rightarrow 2Fe_2O_3\)

By Stoichiometry of the reaction:

4 moles of iron reacts with 3 moles of oxygen gas

So, 0.75 moles of iron will react with = \(\frac{3}{4}\times 0.75=0.5625mol\) of oxygen gas

As, given amount of oxygen gas is more than the required amount. So, it is considered as an excess reagent.

Thus, iron is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

4 moles of iron produces 2 moles of iron (III) oxide

So, 0.75 moles of iron will produce = \(\frac{2}{4}\times 0.75=0.375mol\) of iron (III) oxide

Now, calculating the mass of iron (III) oxide by using equation 1:

Molar mass of iron (III) oxide = 159.7 g/mol

Moles of iron (III) oxide = 0.375 moles

Putting values in equation 1, we get:

\(0.375mol=\frac{\text{Mass of iron (III) oxide}}{159.7g/mol}\\\\\text{Mass of iron (III) oxide}=(0.375mol\times 159.7g/mol)=59.9g\)

Hence, the mass of iron (III) oxide produced is 59.9 grams.