Calculate the pH of a solution made by 1 L buffered solution of 0.635 M NH3 with the addition of 0.10 mol HCl (Kb for NH3 =1.8 ×10–5).

Options are 9.11, 4.02, 8.53, or 9.26.

I think it is 9.11 but I am not sure

Any help is appreciated!

9.11 was the answer!

sorry for the inconvenience