Adding base causes the pH of a solution to increase
pH is a measure of the hydrogen ion concentration of a system. Solutions with a low pH possess a high concentration of hydrogen ions, while solutions with a high pH possess a low concentration of hydrogen ions. To increase the pH of a solution, base can be added to it. Base will release hydroxide ions (OH-) in the solution which will neutralize or reduce the H+ ions concentration in the solution. This way the pH is increased.