HA(aq)+ H2O (l) <-> H3O+(aq)+ A¯ (aq)
Given the reaction above, which of the following will cause an increase in the pH of an equilibrium mixture? Give all answers which apply.
A) add KA B) add HA
C) remove A¯ D) remove HA
E) none of these will affect the pH.
Answer A and D ??
To determine which of the options will cause an increase in the pH of an equilibrium mixture, let's analyze each option.
A) Adding KA:
If you add KA, which is a salt, it will dissociate into its ions in solution. The anion of KA, A¯, is a conjugate base. Adding a conjugate base will shift the equilibrium towards the reactant side (left), reducing the concentration of H3O+ ions, and thus increasing the pH. Therefore, adding KA will increase the pH.
B) Adding HA:
If you add HA, which is the acid in the reaction, it will react with water to produce more H3O+ ions, shifting the equilibrium towards the product side (right). This increase in H3O+ ions will decrease the pH. Therefore, adding HA will decrease the pH, not increase it.
C) Removing A¯:
Removing A¯, the conjugate base, will shift the equilibrium towards the product side (right) to replace the lost A¯ ions. This will result in an increase in H3O+ ions, decreasing the pH. Therefore, removing A¯ will decrease the pH, not increase it.
D) Removing HA:
Removing HA, the acid, will shift the equilibrium towards the reactant side (left) to replace the lost HA molecules. This will decrease the concentration of H3O+ ions and increase the pH. Therefore, removing HA will increase the pH.
E) None of these will affect the pH:
This option is incorrect since, as explained above, adding KA (option A) and removing HA (option D) will cause an increase in the pH.
Therefore, the correct answers are A) add KA and D) remove HA.