Combination Reaction Explained

The question asks to identify the type of chemical reaction involved when calcium oxide reacts with water to produce slaked lime.

Understanding the Reaction

The reaction described is:

Calcium Oxide + Water → Slaked Lime

In chemical terms, this is represented as:

\(CaO\) (Calcium Oxide) + \(H_2O\) (Water) → \(Ca(OH)_2\) (Calcium Hydroxide, commonly known as Slaked Lime)

Let's analyze the characteristics of this reaction:

• Two distinct reactants, \(CaO\) and \(H_2O\), are involved.
• These reactants combine to form a single product, \(Ca(OH)_2\).

A combination reaction is defined as a reaction where two or more simple substances (elements or compounds) combine to form a single, more complex product.

Looking at the reaction \(CaO + H_2O → Ca(OH)_2\), we see that two reactants (calcium oxide and water) join together to form one product (calcium hydroxide). This perfectly matches the definition of a combination reaction.

Analyzing the Options

Let's examine why the other options are not the best fit for this specific reaction:

• Displacement reaction: This type of reaction involves an element replacing another element in a compound (e.g., \(Zn + CuSO_4 → ZnSO_4 + Cu\)). Our reaction doesn't involve one substance displacing another.
• Precipitation reaction: This involves the formation of an insoluble solid (a precipitate) when two solutions are mixed. While calcium hydroxide is only sparingly soluble, the primary characteristic of this reaction is the combination of reactants, not just precipitate formation.
• Decomposition reaction: This is the opposite of a combination reaction, where a single compound breaks down into two or more simpler substances (e.g., \(CaCO_3 → CaO + CO_2\)). The reaction of calcium oxide and water is about forming, not breaking down.

Therefore, the reaction represents a clear example of a combination reaction where calcium oxide and water combine to form slaked lime.