Final answer:
Option 4: Adding NaHCO₃ to the solution will increase the concentration of HCO₃⁻ due to Le Châtelier's principle. The reaction may shift to increase H₂CO₃ concentration slightly, but this is generally not significant.
Step-by-step explanation:
When you add NaHCO₃ to the solution with the acidic equilibrium H₂CO₃(aq) + H₂O(l) ⇌ HCO₃⁻(aq) + H₃O⁺ (aq), the resulting effect can be understood through Le Châtelier's principle. The addition of NaHCO₃ increases the concentration of HCO₃⁻, which is a product of this equilibrium. The concentration of NaHCO₃ in the solution will also increase as it is being directly added.
To re-establish equilibrium, the reaction will shift towards the reactants, which theoretically could increase the concentration of H₂CO₃. However, no significant increase in the concentration of H₂CO₃ is typically observed due to the buffering capacity of this equilibrium system. Adding NaHCO₃ will not increase the concentration of H₃O⁺; instead, it may actually slightly decrease due to the common ion effect. Finally, the concentration of NaHCO₃ will indeed increase because you are directly adding it to the solution.