Problem 31 - Chemistry The Science in Context

Question

How many moles of iron are there in 1 mole of the following compounds? (a). \(\mathrm{FeO} ;\) (b) .\(\mathrm{Fe}_{2} \mathrm{O}_{3} ;\) (c) \(\mathrm{Fe}(\mathrm{OH})_{3}\) (d). \(\mathrm{Fe}_{3} \mathrm{O}_{4}\)

Step-by-Step Solution

Answer

Answer: (a) 1 mole of iron, (b) 2 moles of iron, (c) 1 mole of iron, and (d) 3 moles of iron.

Step 1: (a) Moles of iron in FeO

For \(\mathrm{FeO}\), there is one mole of iron atoms (Fe) and one mole of oxygen atoms (O). Therefore, in 1 mole of \(\mathrm{FeO}\), there are 1 moles of iron atoms (\(\mathrm{Fe}\)).

Step 2: (b) Moles of iron in \(\mathrm{Fe}_{2} \mathrm{O}_{3}\)

In the compound, \(\mathrm{Fe}_{2} \mathrm{O}_{3}\), there are two moles of iron atoms (Fe) and three moles of oxygen atoms (O). Therefore, in 1 mole of \(\mathrm{Fe}_{2} \mathrm{O}_{3}\), there are 2 moles of iron atoms.

Step 3: (c) Moles of iron in \(\mathrm{Fe}(\mathrm{OH})_{3}\)

In the compound, \(\mathrm{Fe}(\mathrm{OH})_{3}\), there is one mole of iron atoms (Fe) and three moles of hydroxide groups (OH). As these groups are not iron, they do not contribute to the number of iron moles. Therefore, in 1 mole of \(\mathrm{Fe}(\mathrm{OH})_{3}\), there is 1 mole of iron atoms.

Step 4: (d) Moles of iron in \(\mathrm{Fe}_{3} \mathrm{O}_{4}\)

In the compound, \(\mathrm{Fe}_{3} \mathrm{O}_{4}\), there are three moles of iron atoms (Fe) and four moles of oxygen atoms (O). Therefore, in 1 mole of \(\mathrm{Fe}_{3} \mathrm{O}_{4}\), there are 3 moles of iron atoms.

Key Concepts

Molecular Composition

Understanding molecular composition is essential for recognizing the makeup of chemical compounds. A molecule consists of atoms that are bonded together in specific ratios to form a unique chemical. For instance, water (H₂O) is always composed of two hydrogen atoms and one oxygen atom.

This composition is represented using chemical formulas. These formulas not only state the types of atoms present but also their quantities, often denoted by subscripts. In iron oxide (FeO), the formula reveals one iron (Fe) atom and one oxygen (O) atom per molecule.

When analyzing molecular composition, look for:

• The elemental symbols, which represent different atoms.
• The numerical subscripts, indicating the number of each type of atom present.
• The overall stoichiometry, which can be deduced from these quantities.

By understanding this, you can accurately calculate entities such as the number of moles of a specific element within a compound, just like determining the number of iron moles in various iron oxides.

Stoichiometry

Stoichiometry is a concept used to relate the quantities of reactants and products in chemical reactions. It involves using balanced chemical equations to understand how substances interact with each other.

In stoichiometry, the concept of moles is vital. A mole is a unit representing a specific number of particles, typically Avogadro's number, which is approximately 6.022 x 10²³. This allows for a common ground when dealing with large numbers of atoms or molecules.

When applied to compounds like Fe₂O₃, stoichiometry helps in determining the number of iron atoms. The formula indicates two iron atoms (or moles per mole of compound) and three oxygen atoms. Thus, 1 mole of Fe₂O₃ contains 2 moles of iron.

To effectively use stoichiometry:

• Identify the proportions of each component in a formula.
• Relate these proportions to moles, using the concept of Avogadro's number if needed.
• Apply these proportions to calculate the moles of specific substances as required by your problem.

By mastering stoichiometry, you can solve problems involving complex chemical reactions and compositions.

Chemical Compounds

Chemical compounds consist of atoms from different elements, bonded together in fixed ratios. This bonding can be ionic, where one atom donates electrons to another, or covalent, where atoms share electrons.

Each compound has unique properties and structures, determined by the types of bonds and the atoms involved. For example, \( ext{Fe(OH)}_3 \) (iron(III) hydroxide) consists of iron, oxygen, and hydrogen atoms, forming complex structures through ionic bonds between iron ions and hydroxide groups.

Recognizing chemical compound types includes understanding:

• The elemental composition, shown in chemical formulas.
• The types of chemical bonds (ionic or covalent).
• The functional groups, like OH in the compound above, which often influence chemical reactivity.

When examining compounds, especially those containing multiple elements like iron oxides, understanding these properties helps determine their chemical behavior, allowing for the accurate calculation of specific components, such as the number of moles of individual elements like iron.