Question

Classify each of the following reactions as a combination, decomposition, single replacement, double replacement, or combustion: a. \(4 \mathrm{Fe}(s)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{Fe}_{2} \mathrm{O}_{3}(s)\) b. \(\mathrm{Mg}(s)+2 \mathrm{AgNO}_{3}(a q) \longrightarrow \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}(a q)+2 \mathrm{Ag}(s)\) c. \(\mathrm{CuCO}_{3}(s) \stackrel{\Delta}{\longrightarrow} \mathrm{CuO}(s)+\mathrm{CO}_{2}(g)\) d. \(\mathrm{NaOH}(a q)+\mathrm{HCl}(a q) \longrightarrow \mathrm{NaCl}(a q)+\mathrm{H}_{2} \mathrm{O}(t)\) e. \(\mathrm{ZnCO}_{3}(s) \stackrel{\Delta}{\longrightarrow} \mathrm{CO}_{2}(g)+\mathrm{ZnO}(s)\) f. \(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+6 \mathrm{KOH}(a q) \longrightarrow\) \(2 \mathrm{Al}(\mathrm{OH})_{3}(s)+3 \mathrm{~K}_{2} \mathrm{SO}_{4}(a q)\) \(\mathrm{g} \cdot \mathrm{Pb}(s)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{PbO}_{2}(s)\) h. \(\mathrm{C}_{4} \mathrm{H}_{8}(g)+6 \mathrm{O}_{2}(g) \stackrel{\Delta}{\longrightarrow} 4 \mathrm{CO}_{2}(g)+4 \mathrm{H}_{2} \mathrm{O}(g)\)

Short answer

a. Combinationb. Single Replacementc. Decompositiond. Double Replacemente. Decompositionf. Double Replacementg. Combinationh. Combustion

Step-by-step solution

- Classify reaction (a)

Analyze the reaction: oindent\(4 \mathrm{Fe}(s)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{Fe}_{2} \mathrm{O}_{3}(s)\)Since two or more reactants combine to form a single product, this is a combination reaction.

- Classify reaction (b)

Analyze the reaction: oindent\(\mathrm{Mg}(s)+2 \mathrm{AgNO}_{3}(a q) \longrightarrow \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}(a q)+2 \mathrm{Ag}(s)\)Since one element replaces another in a compound, this reaction is a single replacement reaction.

- Classify reaction (c)

Analyze the reaction: oindent\(\mathrm{CuCO}_{3}(s) \stackrel{\Delta}{\longrightarrow} \mathrm{CuO}(s)+\mathrm{CO}_{2}(g)\)One compound breaks down into two or more products, this is a decomposition reaction.

- Classify reaction (d)

Analyze the reaction: oindent\(\mathrm{NaOH}(a q)+\mathrm{HCl}(a q) \longrightarrow \mathrm{NaCl}(a q)+\mathrm{H}_{2} \mathrm{O}(t)\)Since ions exchange between two compounds, this reaction is a double replacement reaction.

- Classify reaction (e)

Analyze the reaction: oindent\(\mathrm{ZnCO}_{3}(s) \stackrel{\Delta}{\longrightarrow} \mathrm{CO}_{2}(g)+\mathrm{ZnO}(s)\)One compound breaks down into two or more products, this is a decomposition reaction.

- Classify reaction (f)

Analyze the reaction: oindent\(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+6 \mathrm{KOH}(a q) \longrightarrow 2 \mathrm{Al}(\mathrm{OH})_{3}(s)+3 \mathrm{~K}_{2} \mathrm{SO}_{4}(a q)\)Since ions exchange between two compounds, this reaction is a double replacement reaction.

- Classify reaction (g)

Analyze the reaction: oindent\(\mathrm{Pb}(s)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{PbO}_{2}(s)\)Two reactants combine to form a single product, this is a combination reaction.

- Classify reaction (h)

Analyze the reaction: oindent\(\mathrm{C}_{4} \mathrm{H}_{8}(g)+6 \mathrm{O}_{2}(g) \stackrel{\Delta}{\longrightarrow} 4 \mathrm{CO}_{2}(g)+4 \mathrm{H}_{2} \mathrm{O}(g)\)A hydrocarbon reacts with oxygen to produce carbon dioxide and water, this reaction is a combustion reaction.

Key concepts

Combination Reaction

In a combination reaction, two or more reactants combine to form a single product. For example:

• Reaction (a): \( 4\ \mathrm{Fe}(s) + 3\ \mathrm{O}_{2}(g) \rightarrow 2\ \mathrm{Fe}_{2}\ \mathrm{O}_{3}(s) \) illustrates a combination reaction.

Reactants \( \mathrm{Fe}(s) \) and \( \mathrm{O}_{2}(g) \) merge to make \( \mathrm{Fe}_{2}\ \mathrm{O}_{3}(s) \). Such reactions are simple and are often named synthesis reactions, signaling the creation of new compounds. This includes many everyday processes, like metal rusting.

Decomposition Reaction

A decomposition reaction involves a single compound breaking down into two or more simpler products. Two of our example reactions fall into this category:

• Reaction (c): \( \mathrm{CuCO}_{3}(s) \stackrel{\Delta}{\rightarrow} \mathrm{CuO}(s) + \mathrm{CO}_{2}(g) \)
• Reaction (e): \( \mathrm{ZnCO}_{3}(s) \stackrel{\Delta}{\rightarrow} \mathrm{CO}_{2}(g) + \mathrm{ZnO}(s) \)

Both reactions showcase compounds breaking apart into simpler molecules or elements. Decomposition reactions play a key role in processes like the breakdown of organic matter and various industrial processes, like the production of gases.

Single Replacement Reaction

In a single replacement reaction, an element replaces another element in a compound. This type of reaction is demonstrated below:

• Reaction (b): \( \mathrm{Mg}(s) + 2\ \mathrm{AgNO}_{3}(a q) \rightarrow \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}(a q) + 2\ \mathrm{Ag}(s) \)

Here, \( \mathrm{Mg} \) displaces \( \mathrm{Ag} \) from \( \mathrm{AgNO}_{3} \). These reactions are essential in many applications, such as metal extraction and various synthesis processes. They often involve reactive metals and salts or acids.

Double Replacement Reaction

Double replacement reactions involve the exchange of ions between two compounds, resulting in the formation of two new compounds. Examples include:

• Reaction (d): \( \mathrm{NaOH}(a q) + \mathrm{HCl}(a q) \rightarrow \mathrm{NaCl}(a q) + \mathrm{H}_{2}\ \mathrm{O}(t) \)
• Reaction (f): \( \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q) + 6\ \mathrm{KOH}(a q) \rightarrow 2\ \mathrm{Al}(\mathrm{OH})_{3}(s) + 3\ \mathrm{K}_{2}\ \mathrm{SO}_{4}(a q) \)

These reactions are common in precipitation processes and many natural biochemical pathways. They play a crucial role in various industrial processes, such as water purification.

Combustion Reaction

Combustion reactions involve a hydrocarbon reacting with oxygen to produce carbon dioxide and water. Our example is:

• Reaction (h): \( \mathrm{C}_{4}\ \mathrm{H}_{8}(g) + 6\ \mathrm{O}_{2}(g) \stackrel{\Delta}{\rightarrow} 4\ \mathrm{CO}_{2}(g) + 4\ \mathrm{H}_{2}\ \mathrm{O}(g) \)

These highly exothermic reactions are fundamental to energy production. They occur daily in phenomena like burning fuels, which generate heat and light.

Combustion reactions are vital for power plants, internal combustion engines, and even cellular respiration, highlighting their ubiquitous presence in daily life and technology.