Which of the following equations represents a single replacement reaction?

A. [tex]FeS_{(s)} + 2HCl_{(aq)} \longrightarrow H_2S_{(g)} + FeCl_2_{(aq)}[/tex]
B. [tex]2HgO_{(s)} \longrightarrow 2Hg_{(l)} + O_2_{(g)}[/tex]
C. [tex]2Sb_{(s)} + 3I_2_{(s)} \longrightarrow 2SbI_3_{(s)}[/tex]
D. [tex]Zn_{(s)} + H_2SO_4_{(aq)} \longrightarrow ZnSO_4_{(aq)} + H_2_{(g)}[/tex]



Answer :

To determine which of the given equations represents a single replacement reaction, let's first understand the different types of chemical reactions:

1. Single Replacement Reaction: One element replaces another element in a compound.
2. Decomposition Reaction: A compound breaks down into simpler compounds or elements.
3. Synthesis Reaction: Two or more simple substances combine to form a more complex substance.

Now, let's analyze each equation step by step:

- Equation a: [tex]\( \text{FeS (s) + 2 HCl (aq) → H}_2\text{S (g) + FeCl}_2\text{ (aq)} \)[/tex]
- Here, iron (Fe) in FeS replaces hydrogen (H) in HCl forming H[tex]\(_2\)[/tex]S and FeCl[tex]\(_2\)[/tex].
- This is a single replacement reaction.

- Equation b: [tex]\( \text{2 HgO (s) → 2 Hg (l) + O}_2\text{ (g)} \)[/tex]
- Here, mercury(II) oxide (HgO) decomposes into mercury (Hg) and oxygen (O[tex]\(_2\)[/tex]).
- This is a decomposition reaction.

- Equation c: [tex]\( \text{2 Sb (s) + 3 I}_2\text{ (s) → 2 SbI}_3\text{ (s)} \)[/tex]
- Here, antimony (Sb) combines with iodine (I[tex]\(_2\)[/tex]) to form antimony triiodide (SbI[tex]\(_3\)[/tex]).
- This is a synthesis reaction.

- Equation d: [tex]\( \text{Zn (s) + H}_2\text{SO}_4\text{ (aq) → ZnSO}_4\text{ (aq) + H}_2\text{ (g)} \)[/tex]
- Here, zinc (Zn) replaces hydrogen (H) in sulfuric acid (H[tex]\(_2\)[/tex]SO[tex]\(_4\)[/tex]), forming zinc sulfate (ZnSO[tex]\(_4\)[/tex]) and hydrogen gas (H[tex]\(_2\)[/tex]).
- This is a single replacement reaction.

Based on the analysis above, the equations that represent single replacement reactions are:
- Equation a: [tex]\( \text{FeS (s) + 2 HCl (aq) → H}_2\text{S (g) + FeCl}_2\text{ (aq)} \)[/tex]
- Equation d: [tex]\( \text{Zn (s) + H}_2\text{SO}_4\text{ (aq) → ZnSO}_4\text{ (aq) + H}_2\text{ (g)} \)[/tex]

Therefore, the correct choices are:
1. Equation a
2. Equation d