How much 0.521 M NaOH will be needed to raise the pH of 0.161 L of 4.51 M ascorbic acid (H2C6H6O6) to a pH of 11.60? Solution pH of acidic buffer = pka2 + log(salt/acid) No of mol of ascorbic acid = 0.161*4.51 = 0.726 mol No of mol of salt = x mol pka2 = 11.6, pH = 11.6 11.6 = 11.6 + log(x/(0.726-x)) x = 0.363 NO of mol of NaOH required = 2x = 2*0.363 = 0.726 mol volume of NaOH must take = 0.726/0.521 = 1.4 L answer: 1.4 L.

1. How much 0.521 M NaOH will be needed to raise the pH of 0.161 L of 4.51 M ascorbic acid
(H2C6H6O6) to a pH of 11.60?
Solution
pH of acidic buffer = pka2 + log(salt/acid)
No of mol of ascorbic acid = 0.161*4.51 = 0.726 mol
No of mol of salt = x mol
pka2 = 11.6, pH = 11.6
11.6 = 11.6 + log(x/(0.726-x))
x = 0.363
NO of mol of NaOH required = 2x = 2*0.363 = 0.726 mol
volume of NaOH must take = 0.726/0.521 = 1.4 L
answer: 1.4 L