Question

What is the pOH of a solution that has OH concentration equal to `1.36×10^-10" mol"*"dm"^(-3)` ?

Answer 1

`"pOH"=9.866`

Explanation:

By definition
`"pOH"=-log_(10)["OH"^-]`
where `["OH"^-]` is the hydroxide ion concentration of the solution in `"M"` or `"mol"*"dm"^(-3)`, moles per cubic decimeter, or equivalently moles per liter.

Substituting `["OH"^-]=1.36*10^(-10)" mol"*"dm"^(-3)`,
`"pOH"=9.866`.

Note that by convention the number of decimal places the `"pOH"` value has shall equal to the number of significant figures in the value of `["OH"^-]`. `["OH"^-]` has `3` significant figures, which correspond to three decimal places for the `"pOH"` measurement.