Q.
20mL of M/10CH3COOH solution is titrated with M/10NaOH solution. After addition of 16mL solution of NaOH. What is the pH of the solution (pKa=4.47)
mEq of CH3COOH=20×101=2 mEq of NaOH=16×101=1.6
So 1.6mEq of NaOH reacts with 1.6mEq of CH3COOH to form 1.6mEq of salt CH3COONa and (2−1.6=0.4mEq) of WA(CH3COOH) is left and an acidic buffer is formed. So to calculate pH, buffer equation is used pH=pKa+log( Acid Salt )=4.74+log(0.41.6) =4.74+2log2 =4.74+2×0.3010=5.35