Let's analyze the chemical reaction:
[tex]\[ C_6H_5OH (aq) + H_2O (l) \longrightarrow C_6H_5O^- (aq) + H_3O^+ (aq) \][/tex]
We need to determine which reactant acts as an acid, meaning it donates a proton (H^+) to the solution and thereby increases the concentration of [tex]\( H_3O^+ \)[/tex] ions.
1. Identify the role of each species:
- [tex]\( C_6H_5OH \)[/tex] (phenol) in the aqueous phase (aq)
- [tex]\( H_2O \)[/tex] (water) in the liquid phase (l)
- [tex]\( C_6H_5O^- \)[/tex] (phenoxide ion) in the aqueous phase (aq)
- [tex]\( H_3O^+ \)[/tex] (hydronium ion) in the aqueous phase (aq)
2. Write down the description of an acid:
- An acid is a substance that donates a proton (H^+).
3. Examine the reaction:
- On the reactants' side, we have [tex]\( C_6H_5OH \)[/tex] and [tex]\( H_2O \)[/tex].
- On the products' side, we have [tex]\( C_6H_5O^- \)[/tex] and [tex]\( H_3O^+ \)[/tex].
4. Determine where the proton (H^+) comes from:
- [tex]\( C_6H_5OH \)[/tex] donates a proton (H^+), transforming into [tex]\( C_6H_5O^- \)[/tex].
- The [tex]\( H^+ \)[/tex] donated by [tex]\( C_6H_5OH \)[/tex] combines with [tex]\( H_2O \)[/tex] to form [tex]\( H_3O^+ \)[/tex].
5. Conclusion:
- Since [tex]\( C_6H_5OH \)[/tex] is the substance that donates the proton (H^+) and increases the concentration of [tex]\( H_3O^+ \)[/tex] in the solution, it acts as an acid in this reaction.
Thus, [tex]\( C_6H_5OH (aq) \)[/tex] is the reactant that acts as an acid by contributing an [tex]\( H^+ \)[/tex] ion to create [tex]\( H_3O^+ \)[/tex] in the chemical equation.
The correct answer is:
[tex]\[ \boxed{C_6H_5OH (aq)} \][/tex]
