Question

1. Calculate and formulate an ophthalmic buffer solution of boric acid (pKa=9.24) and sodium borate. To make it pH 9.0 with buffer capacity of 0.02, the molar concentrations of boric acid should be ____Mol/L.

2. And the molar concentration of and sodium borate should be ___Mol/L.

Answer 1

Solution, Let, us Consides a buffer is made aweak auid wih bmole of a str ong base m Hhe mixture Gncen tna Hon of weaK auid Ca = a-b) mellL amd Cen Centna tion of Salt. Csbme/LAcconding to Hender son euation, tue PH of this buffer mixture is mole of wure alb pH- pka + a-b pKaan6 + 2.303 egua ton (1) a-b Since, Ka is the ionisation Constort of the weak acid) Differ em tng the alove ex Pnession with nes pech to 6 we a-b)1-61) (a-6)2 dPH a-b 0+ 2.303 a (a- b) 2.303 bla-6)2 a I .303 b (a-6) Inveting thi's ex Pression gives theufee Gpacity() 6(a-6) 2.30 3 2uahion (2). a The given values- pka - 9.24 PH-9.0 002 Puing te value in ezua tion ) 90=9.24 + 2.303 a-b 2.303 x (9.0-9.24 CodarcHod =0.553. a-b 0.575 a-0.575 b b C.575 a-b a = 2.74b 1575b O.575 a tv, b- 0.365

Puing he value in egua tion (2) - b(a-b) 2.30 3 a 6(a-6) 8-684 x 10- 3 1 a vaue of b we Hue Pu 0.365 (a-0.365a) 8.68yx10-3 8.684X10- 3 O.635 0 = O.365 8.684X10-3 0.0375 O.365 X0 635 O. O137 b=0.36 5X0.0375= ot . Henee, tue initia molan Cen centration bonic auid should be O.0375 MOL L in the mixtune( Buffer Selu hon) Concentralion Cmd G borie aud (0,0375-0.01I 37) = 0.0238 moL/L 2The molon Con cen trahion of cmd Sodium bona te gloul d be 0. 0137 MOL/L
​​​​​​