When weak base solution `(50mL of 0.1 N NH_(4)OH)` is titrated with strong acid `(0.1N HCI)`, the `pH` of the solution initially decrease fast and then decreases slowely till near the equivalence point (as shown in figure). Which of the following is//are correct.

Options

A. The initial fast decrement in `pH` is due to fast consumption of free `OH^(-)` ions by `HCl`
B. The slow decreases of `pH` is due to formation of an acidic buffer solution after addition of some`HCl`
C. The slope of shown `pH` graph (magnitude only) will be minimum when `25mL` of `0.1 M HCl` is added.
D. The slow decreases of `pH` is due to formation of a basic buffer solution after addition of some `HCl`.

Explanation

Initial decrement is due to consumptionof free `OH^(-)` ions, then slow decrement in `pH` is due basic buffer solution and minimum slope will be there whenthere is best buffer action `(["salt"]/["Base"]=1)`