Let's analyze the given chemical reaction:
[tex]\[
4 Fe + 3 O_2 + x H_2 O \rightarrow 2 Fe_2 O_3 \cdot x H_2 O
\][/tex]
The formation of rust involves the following components:
- Iron (Fe): A metal element.
- Oxygen (O_2): A diatomic molecule.
- Water (H_2O): In the form of water vapor or moisture.
To classify the reaction, let's explore each type mentioned in the question:
1. Synthesis Reaction:
A synthesis reaction involves two or more reactants combining to form a single product.
In the given equation, iron (Fe) and oxygen (O_2), along with water (H_2O), combine to form iron oxide (rust). This fits the definition of a synthesis reaction.
2. Combustion Reaction:
Combustion reactions typically involve a substance reacting with oxygen, releasing energy in the form of heat and light. Although the equation doesn't explicitly show heat and light being released, the reaction with oxygen indicates it can be classified under combustion reactions. Hence, the formation of rust aligns with the characteristics of a combustion reaction involving oxygen.
3. Decomposition Reaction:
Decomposition reactions involve a single compound breaking down into two or more simpler substances. The given equation is not decomposing a single substance but rather combining multiple substances.
4. Single Replacement Reaction:
Single replacement reactions involve one element replacing another in a compound. In the given reaction, there is no replacement of iron or oxygen by another element.
5. Double Replacement Reaction:
Double replacement reactions involve the exchange of ions between two compounds to form two new compounds. This is not occurring in the given reaction where reactants are combining to form a product rather than exchanging parts.
Given this analysis, the correct classification of the given reaction fits under:
- Synthesis Reaction (as iron and oxygen combine to form iron oxide).
- Combustion Reaction (as it involves a reaction with oxygen).
Thus, the given reaction is best classified as:
- Synthesis reaction.
Conclusively, the correct answer is:
- [tex]\(\boxed{1} \text{ (synthesis)}\)[/tex]
