To determine which reaction is a decomposition reaction, let's first define what a decomposition reaction is. A decomposition reaction is a type of chemical reaction where one compound breaks down into two or more simpler substances. The general form of a decomposition reaction is:
[tex]\[ AB \rightarrow A + B \][/tex]
Now, let's analyze each given reaction to see if it fits the definition of a decomposition reaction.
Option A:
[tex]\[ 2 KClO_3 \rightarrow 2 KCl + 3 O_2 \][/tex]
In this reaction, potassium chlorate ([tex]\( KClO_3 \)[/tex]) breaks down into potassium chloride ([tex]\( KCl \)[/tex]) and oxygen gas ([tex]\( O_2 \)[/tex]). This fits the definition of a decomposition reaction, as a single compound [tex]\( 2 KClO_3 \)[/tex] decomposes into two simpler substances, [tex]\( 2 KCl \)[/tex] and [tex]\( 3 O_2 \)[/tex].
Option B:
[tex]\[ 4 Na + O_2 \rightarrow 2 Na_2O \][/tex]
In this reaction, sodium ([tex]\( Na \)[/tex]) and oxygen ([tex]\( O_2 \)[/tex]) combine to form sodium oxide ([tex]\( Na_2O \)[/tex]). This is a combination reaction, not a decomposition reaction, because two elements combine to form a compound.
Option C:
[tex]\[ ZnS + 3 O_2 \rightarrow 2 ZnO + 2 SO_2 \][/tex]
In this reaction, zinc sulfide ([tex]\( ZnS \)[/tex]) reacts with oxygen gas ([tex]\( O_2 \)[/tex]) to form zinc oxide ([tex]\( ZnO \)[/tex]) and sulfur dioxide ([tex]\( SO_2 \)[/tex]). This is a combustion reaction, not a decomposition reaction, because it involves the reaction of a compound with oxygen.
Option D:
[tex]\[ 2 NaBr + CaF_2 \rightarrow 2 NaF + CaBr_2 \][/tex]
In this reaction, sodium bromide ([tex]\( NaBr \)[/tex]) and calcium fluoride ([tex]\( CaF_2 \)[/tex]) exchange ions to form sodium fluoride ([tex]\( NaF \)[/tex]) and calcium bromide ([tex]\( CaBr_2 \)[/tex]). This is a double displacement reaction, not a decomposition reaction.
Based on the definitions and analysis, we can conclude that the correct answer is:
A. [tex]\( 2 KClO_3 \rightarrow 2 KCl + 3 O_2 \)[/tex]
This reaction is indeed a decomposition reaction.
