Certainly! To understand how the amount of unionized acid HA changes under different conditions, we need to consider the principles of chemical equilibrium and Le Chatelier's Principle for the equilibrium reaction:
[tex]\[ HA + H_2O \leftrightarrow H_3O^+ + A^- \][/tex]
Let's analyze each given scenario step-by-step.
### a. The solution is diluted with water
Effect: Increased
When the solution is diluted with water, it effectively decreases the concentrations of all species in the solution. According to Le Chatelier's Principle, the equilibrium will shift to counteract this disturbance. Hence, the equilibrium will shift to the right, producing more [tex]\( H_3O^+ \)[/tex] and [tex]\( A^- \)[/tex] ions to increase the ion product. This shift results in a greater extent of ionization of HA, thereby increasing the amount of unionized HA as more of the acid dissociates.
### b. A strong acid like HCl is added to the solution
Effect: Decreased
Adding a strong acid such as HCl increases the concentration of [tex]\( H_3O^+ \)[/tex] ions in the solution. According to Le Chatelier's Principle, the equilibrium will shift to the left to reduce the increase in [tex]\( H_3O^+ \)[/tex] concentration. This backward shift in equilibrium leads to more [tex]\( H_3O^+ \)[/tex] and [tex]\( A^- \)[/tex] combining to reform HA, thereby decreasing the amount of unionized HA as the equilibrium moves towards the reactants' side.
### c. The soluble ionic salt, NaA, is added to the solution
Effect: Decreased
Adding a soluble ionic salt like NaA increases the concentration of the [tex]\( A^- \)[/tex] ions in the solution, which is the conjugate base of the weak acid HA. According to Le Chatelier's Principle, the system will shift the equilibrium to the left to counteract the addition of [tex]\( A^- \)[/tex]. By shifting left, more [tex]\( H_3O^+ \)[/tex] and [tex]\( A^- \)[/tex] combine to form HA, reducing the amount of unionized HA because the equilibrium now favors the reactants more.
### d. A strong soluble base such as NaOH is added to the solution
Effect: Increased
Adding a strong base such as NaOH increases the concentration of [tex]\( OH^- \)[/tex] ions in the solution. [tex]\( OH^- \)[/tex] ions react with [tex]\( H_3O^+ \)[/tex] ions to form water, effectively decreasing the concentration of [tex]\( H_3O^+ \)[/tex]. According to Le Chatelier's Principle, the equilibrium will shift to the right to produce more [tex]\( H_3O^+ \)[/tex]. This shift to the right leads to more dissociation of HA into [tex]\( H_3O^+ \)[/tex] and [tex]\( A^- \)[/tex], thereby increasing the amount of unionized HA.
### Summary of the Effects:
- Dilution with water: Increased
- Adding HCl: Decreased
- Adding NaA: Decreased
- Adding NaOH: Increased
These effects align with our understanding of how equilibrium adjustments respond to different perturbations according to Le Chatelier's Principle.
