100mL of `pH =6` solution is diluted to 100mL by water. pH of the solution will increase by

Options

A. 9
B. 1
C. `0.7`
D. `0.3`

Answer

C

Explanation

Before dilution `, [H^(+)]=10^(-6)M`
`:. [H^(+)]` from acid `10^(-6)-10^(-7)=0.9xx10^(-6)M`
`M_(1)V_(1)=M_(2)V_(2)`
`0.9 xx 10^(-6)xx100=1000xxM_(2)`
`M_(2)=0.9 xx 10^(-7)M`
After dilution,
Total `[H^(+)]=[H^(+)]` from acid `= [H^(+)]` from water
`=0.9 xx 10^(-7) M +10^(-7)M`
`=1.9 xx 10^(-7)M`
`pH =-log [H^(+)]=-log 1.9 xx 10^(-7)`
`=7-lo g 1.9 ~~7-0.3 =6.7 `
`:.` Increase in pH `=6.7 -6`