Calculate the pH of (a) `0.0001 MHCl` solution (b) `0. 04 MHNO _(3)` solution, assuming complete dissociation in each case.

Explanation

(a) Concentration of `HCl = 0.0001 M `
Since HCl is completely dissociated, `[H ^(+)]=0.0001 mol dm (-3)`
`pH =- log [ H ^(+)] =- log [0.0001]=4`
(b) Concentrtaion of `HNO _(3) = 0.04 M `
Since `HNO _(3)` is completely dissociated, `[H ^(+)] = 0.04 mol dm ^(-3)`
`pH =- log [H ^(+)] =- log [0.04] = 1. 398`