Biochemistry Question

Question

1. If 2 mL of 0.5 M NaOH is added to 50 mL of 0.1 M sodium phosphate buffer at pH 7.0, what is the resulting pH?
2. If 5 mL of 0.1 M HCl is added to 50 mL of 0.1 M sodium phosphate buffer at pH 7.0, what is the resulting pH?

Answer 1

The key is to see that this is a Henderson-Hasselbalch equation problem, calculate the moles of phosphate species initially that gave you a pH 7.0,and recognize that hydroxide and HCl will completely with the acid and conjugate base to convert to the base and acid. then recalculate the pH with the new ratio of base to acid.