Quick Acid/Base Buffer Question (1 Viewer)

[Jojofelyx]

Which of the options below correctly describes what happens when a small amount of strong acid is added to a buffer consisting of the weak acid HA and its conjugate base A-?

A: The concentration of OH- remains the same and the concentration of HA increases.
B: The concentration of OH- increases and the concentration of HA increases.
C: The concentration of OH- decreases and the concentration of HA increases.
D: The concentration of OH- decreases and the concentration of HA decreases.
E: The concentration of OH- remains the same and the concentration of HA decreases.

 

[VeryBoredOfStudies]

C?

 

[Jojofelyx]

C?

The answers do say this but why's that?

 

[Duskheaven]

The answers do say this but why's that?

A strong acid is added. This means to counteract the change in pH, the base (A-) in the buffer has to react with the H+ to reduce the H+ concentration.

A- + H -> HA

The product is HA. Therefore HA increases.

OH decreases because the solution still becomes more acidic when you add the acid. Any OH in solution will be more likely to react with H since there is more H in solution.