Select the correct answer.

Which reaction is a decomposition reaction?

A. [tex]2 KClO_3 \rightarrow 2 KCl + 3 O_2[/tex]
B. [tex]4 Na + O_2 \rightarrow 2 Na_2O[/tex]
C. [tex]ZnS + 3 O_2 \rightarrow 2 ZnO + 2 SO_2[/tex]
D. [tex]2 NaBr + CaF_2 \rightarrow 2 NaF + CaBr_2[/tex]



Answer :

To identify which reaction is a decomposition reaction, let’s first understand 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.

Now, let's examine the given chemical reactions one by one:

A. [tex]\(2 KClO_3 \rightarrow 2 KCl + 3 O_2\)[/tex]

- Here, potassium chlorate ([tex]\(KClO_3\)[/tex]) is breaking down into potassium chloride ([tex]\(KCl\)[/tex]) and oxygen ([tex]\(O_2\)[/tex]).
- This indicates that one compound, [tex]\(2 KClO_3\)[/tex], is decomposing into multiple simpler substances, [tex]\(2 KCl\)[/tex] and [tex]\(3 O_2\)[/tex].

B. [tex]\(4 Na + O_2 \rightarrow 2 Na_2O\)[/tex]

- In this reaction, sodium ([tex]\(Na\)[/tex]) and oxygen ([tex]\(O_2\)[/tex]) are combining to form sodium oxide ([tex]\(Na_2O\)[/tex]).
- This is a combination (or synthesis) reaction, not a decomposition reaction.

C. [tex]\(ZnS + 3 O_2 \rightarrow 2 ZnO + 2 SO_2\)[/tex]

- Here, zinc sulfide ([tex]\(ZnS\)[/tex]) is reacting with oxygen ([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.

D. [tex]\(2 NaBr + CaF_2 \rightarrow 2 NaF + CaBr_2\)[/tex]

- In this reaction, sodium bromide ([tex]\(NaBr\)[/tex]) reacts with calcium fluoride ([tex]\(CaF_2\)[/tex]) 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 the examination of each reaction, the correct decomposition reaction is:

A. [tex]\(2 KClO_3 \rightarrow 2 KCl + 3 O_2\)[/tex]

Therefore, the correct answer is A.