(1). What will be the pH when 50.0 ml of 2.00M carbonic acid is mixed 20.0 ml of 3.00 M sodium bicarbonate? The Ka of carbonic is 4.30 x 10-7. (5 pts) (2). For the buffer system in Problem no. 1, what will be the pH when (a) 15.0 ml of 0.500 M HCl and (b) when 15.0 ml of 0.750 M NaOH is added to the buffer? (10 pts) (3) How will you prepare 500 ml of 0.750 M citrate buffer with pH of 4.25 from solid citric acid (C6H8O7) and solid sodium citrate (Na3C6H5O7). The Ka of citric acid is 7.40 x 104. (15 pts) [Atomic weight: C = 12.01 amu, H = 1.00 amu, O = 16.00 amu, Na = 23.00 amu]