The hydrogen ion concentration would decrease.

Explanation:

* Strong Acids: Strong acids completely ionize in solution, meaning they release all of their hydrogen ions (H+) into the solution.

* Hydroxide Ions: Hydroxide ions (OH-) are the base component of water. They are strong bases.

* Neutralization: When a strong acid and a strong base react, they neutralize each other. This means the hydrogen ions (H+) from the acid react with the hydroxide ions (OH-) from the base to form water (H2O).

Reaction:

H+ (from acid) + OH- (from base) → H2O

Result:

* The addition of hydroxide ions will directly consume hydrogen ions in the solution, reducing their concentration.

* Since the acid and base react in a 1:1 ratio, if you add an equal number of hydroxide ions to hydrogen ions, the solution will become neutral.

* If you add more hydroxide ions than hydrogen ions, the solution will become basic.

Important Note: The final pH of the solution will depend on the initial concentration of the strong acid and the amount of hydroxide ions added.