pH of an aqueous solution of HCl =3.0 . How many moles of `H_3O` or `OH^-` ions are to be added per litre of this solution in order to increase its pH from 3.0 to 3.4?

Explanation

30mL `0.2(N)H_2SO_4-=20mL0.1(M)H_2SO_4`
Similarly 20mL
`0.3(N)(H_2SO_4`
`[:.H_2SO_4` is dibasic normally =`2xx` molarity]
30mL 0.1(M) `H_2SO_4-=0.1xx30-=` 3million mol `H_2SO_4` and 20 mL 0.15(M) `H_2SO_4-=` 3 million mol `H_2SO_4` . Hence total number of million moles of `H_2SO_4` in the mixed solution `=(3+3)=6`
Total volume of the mixed solution = ( 30 + 20) = 50 mL Therefore, molar concentration of `H_2SO_4` in the mixed solution `=6/(50)=0.12(M)`. [ `:'` no. of million moles=malarity `xx` volume (mL)]
In the mixed solution, concentration of `H_3O^+` ion produced from `H_2SO_4=2xx0.12=0.24(M)`
`[H_2SO_4(aq)+2H_2O(l)to2H_3O^+(aq)+SO_4^(2-)(aq)]`
`:.` pH of the mixed solution`=-log_(10)(0.24)=0.62`