Calculate the pH of the mixture formed by the addition of `5,9,9.5,9.9,9.95,10,10.05` and `10.1` mL of `0.5MKOH` solution to 100 mL of `0.05 HBr` solution. What will be the most suitable indicator for this titration ?

Explanation

(i) Meq. of KOH in mixture `= 5xx0.5=2.5`
Meq. of HBr in mixture `100xx0.05=5`
`:."Meq. of HBr left in mixture "=5-2.5=2.5`
`:. M_(HBr) of N_(HBr)= (2.5)/(105)=0.0238`
`("Total volume"=5+100=105)`
`:. [H^(+)]=0.0238`
`:. pH= -log[H^(+)]= -log 2.38xx10^(-2)=1.62`
Proceed similary for other cases:
(ii) `pH=2.34`, (iii) `pH=2.64`, (iv) `3.34`, (v) `7.0`, (vi) `10.35`, (vii) `10,66`.
Indicator used is phenolphtalein.