Question

1. What is the pH of a 1.0L buffer that is 0.10 M in Naz HPO4 and 0.15 M in NaH2PO4? Write the equilibrium reaction equation and corresponding Ka expression for the buffer. K for H2PO4 is 6.2 X 108 2. A 10.00 mL sample of 0.300 M NH3 is titrated with 0.100 M HCl(aq). What is the initial pH? Calculate the pH after the addition of 10.0, 200, 30.0 and 40.0 mL of HCI. Ko for NH3 is 1.8 X 10. 3. What mass of NaOH(s) must you add to a 1.00 L sample of 0.115 M acetic acid (Ka = 1.8 X 10') to produce a solution with a pH of 3.25? 4. Show by calculation why acetic acid (K = 1.8 X 10'), when combined with NaC,H,O, as a buffer, will not produce a pH of 9.00.

I need help with #4. "show by calculation why acetic acid (Ka = 1.8 X 10^-5), when combined with NaC2H3O3 as a buffer, will not produce a pH o 9.00"

Answer 1

4* Given Ka 1.8 x 1o-5 log (Ka) av a (g-0lx 3-1) Co 4.74 Acetic acid uoined oi H S0aium acetate to broduce acidic but er S0dium acetate Na Ha 03 Dave An acidic butten cam Ynev er pH gneater than ar Acconding to the Penderson tfm Nat3 02 = pka tlog P

Now it that the ass ume pH be 9 Thus 4.1 4 t lo9 log 9-4. 74 4.26 4.26 0 12147 So, this is not possible fon outfer so lutom to have value f a Na H0 ~ 18147 S0 the donfer 50lution oi YD t acidi e bnffer it PH aaays less than As, it is an 7 oill ave au