Answer: A weak acid titrated by a strong base
Step-by-step explanation:
The graph refers to the titration of a weak acid such as Hydrofluoric acid with a strong base such as Sodium Hydoxide. What happens is that as the process begins, the pH rises quickly as there is little resistance to the base.
After some time the solution formed begins to act as a buffer between the remaining acid and the base. This reduces the pH change rate and will continue until the base overcomes the solution's buffering capacity.
The Equivalence point which is where the acid will be at it's base form, will be at a pH of 8.6.
I have attached a graph showing the process for better understanding.