To determine which formula equation shows a reversible reaction, we need to look for an equation that involves the double arrow symbol (↔ or [tex]\(\leftrightarrow\)[/tex]), which indicates that the reaction can proceed in both the forward and backward directions.
Let's analyze each of the given equations:
1. [tex]\(2 Na + F_2 \rightarrow 2 NaF\)[/tex]
- This is a one-way reaction where sodium (Na) reacts with fluorine (F_2) to form sodium fluoride (NaF). There is no indication of reversibility.
2. [tex]\(CaCO_3 \rightarrow CaO + CO_2\)[/tex]
- This equation represents the thermal decomposition of calcium carbonate (CaCO_3) into calcium oxide (CaO) and carbon dioxide (CO_2). Again, there is no indication of reversibility here.
3. [tex]\(NH_4Cl (s) \leftrightarrow NH_3(g) + HCl (g)\)[/tex]
- This equation has the double arrow ([tex]\(\leftrightarrow\)[/tex]) symbol, indicating that the solid ammonium chloride (NH_4Cl) can dissociate into ammonia (NH_3) and hydrogen chloride (HCl) gases, and it can also recombine back into solid ammonium chloride. This is a reversible reaction.
4. [tex]\(2 H_2O_2 (aq) \xrightarrow{Pl} 2 H_2O (l) + O_2 (g)\)[/tex]
- This is a one-way reaction where hydrogen peroxide (H_2O_2) decomposes to form water (H_2O) and oxygen (O_2). The arrow indicates that the reaction proceeds in only one direction.
Thus, the equation that shows a reversible reaction is:
[tex]\(NH_4Cl (s) \leftrightarrow NH_3(g) + HCl (g)\)[/tex]
Therefore, the correct answer is option 3.
