The correct option is A 5.22
mmol of CH3COONa=20×0.2=4
mmol of HCl=10×0.1=1
CH3COONa (aq)+HCl (aq)→CH3COOH (aq)+NaCl (l)Initial: 4 1 0 0Final: 3.0 0 1 1
After titration we can see that 3.0 mmol of CH3COONa and 1 mmol of CH3COOH are present. So , the resultant solution will act as an buffer.
Final concentration=Moles Total Volume
Total Volume =20+10=30 mL
[CH3COOH]final=130 M
[CH3CONa]final=330 M
The formula to calculate the pH of an acidic buffer is :
pH=pKa+log([CH3COONa][CH3COOH])pH=4.74+log⎛⎝330130⎞⎠pH=4.74+log(3)=4.74+0.48pH=5.22