Identify the type of each of the following reactions, stating the reason for your answers.
A. [tex]$Fe _2 O _3+2 Al \rightarrow Al _2 O _3+2 Fe +$[/tex] heat
B. [tex]$Pb \left( NO _3\right)_2+2 KI \rightarrow PbI _2(\downarrow)+2 KNO _3$[/tex]
Answer (2)
Reaction A is a single replacement reaction because aluminum replaces iron in iron oxide.
Reaction B is a double replacement reaction because lead(II) nitrate and potassium iodide exchange ions to form lead(II) iodide and potassium nitrate.
Single replacement reactions involve one element replacing another in a compound.
Double replacement reactions involve the exchange of ions between two reactants to form two new compounds.
The types of the reactions are: Reaction A - single replacement, Reaction B - double replacement.
Explanation
Problem Analysis We are given two chemical reactions and we need to identify the type of each reaction and explain the reasoning behind our classification.
Analyzing Reaction A Reaction A: F e 2 O 3 + 2 A l → A l 2 O 3 + 2 F e + heat . In this reaction, aluminum (Al) replaces iron (Fe) in iron oxide ( F e 2 O 3 ). This indicates a single replacement reaction. The presence of heat as a product further supports this classification.
Analyzing Reaction B Reaction B: P b ( N O 3 ) 2 + 2 K I → P b I 2 ( ↓ ) + 2 K N O 3 . In this reaction, the lead(II) ions ( P b 2 + ) from lead(II) nitrate ( P b ( N O 3 ) 2 ) combine with iodide ions ( I − ) from potassium iodide ( K I ) to form lead(II) iodide ( P b I 2 ), which is insoluble and precipitates out of the solution. The nitrate ions ( N O 3 − ) and potassium ions ( K + ) combine to form potassium nitrate ( K N O 3 ). This is a double replacement reaction because the cations and anions of two reactants switch places to form two new compounds. The formation of a precipitate ( P b I 2 ( ↓ ) ) is a characteristic of double replacement reactions.
Conclusion Therefore, Reaction A is a single replacement reaction, and Reaction B is a double replacement reaction.
Examples
Single and double replacement reactions are fundamental concepts in chemistry with real-world applications. For example, single replacement reactions are used in the extraction of metals from their ores, such as the extraction of copper using iron. Double replacement reactions are used in water treatment to remove unwanted ions, such as the removal of lead ions by adding phosphate to form insoluble lead phosphate.
Reaction A is classified as a single replacement reaction because aluminum replaces iron in iron oxide. Reaction B is classified as a double replacement reaction because lead(II) nitrate and potassium iodide exchange ions to form lead(II) iodide and potassium nitrate.
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