50 ml of `1 M CH_(3)COOH` solutioin, when added to 50 ml of 0.5 M NaOH gives a solution with a pH value 'X'. Find the valuer of `'X', pK_(a)` of acetic acid is 4.8.

Explanation

Acetic acid reacts with sodium hydroxide to form sodium acetate.
`CH_(3)COOH+NaOH to CH_(3)COONa+H_(2)O`
No. of milimoles of `CH_(3)COOH=50xx1=50`
no. of milimoles of `NaOH=50xx0.5=25`
No. of millimoles of `CH_(3)COOH` remained unreacted `=50-25=25`
Total Vol. of solution `=50+50=100 ml`
Nol. of millimoles of `CH_(3)COONa` formed =25
`:.` Molarity of `CH_(3)COONa=(25)/(100)=25M`
Molarity of `CH_(3)COOH =(25)/(100)=25M`
`pH=pK_(a)+"log" (["Salt"])/(["Acid"])`
`=4.8+"log" (25)/(25)=4.8+log(1)`
`:. pH` of the solution `=4.8+0=4.8`