Question

An acidic solution has a pH of 4.02. What is the `H_3O^+` concentration of this solution in M?

Answer 1

`H_3O^+=9.55xx10^-6*mol*L^-1`

Explanation:

By definition, `pH=-log_(10)[H_3O^+]`

And thus if `pH=4.02`, `[H_3O^+]=10^(-4.02)` `=` `9.55xx10^-6*mol*L^-1`.

Back in the day, before the advent of cheap electronic calculators, A level students routinely used log tables to aid complex multiplications and divisions. See here and elsewhere.