Question

The [`H^+`] in a solution is 0.01 M. What is the pH of the solution?

Answer 1

`"pH" = 2`

Explanation:

The pH of a given solution is nothing more than the negative log base `10` of the concentration of hydrogen ions, `"H"^(+)`, which you'll sometimes see written as `"H"_ 3"O"^(+)`, the hydronium ion.

You thus have

`color(blue)(ul(color(black)("pH" = - log(["H"^(+)]))))`

In your case, the problem provides you with the concentration of hydrogen ions

`["H"^(+)] = "0.01 M"`

This means that the pH of the solution will be

`"pH" = - log(0.01)`

`"pH" = - log(10^(-2)) = - (-2) * log(10)`

Since you know that

`log_(10)(10) = log(10) = 1`

you can say that

`color(darkgreen)(ul(color(black)("pH" = - (-2) * 1 = 2)))`

Because the pH is `<7`, this solution will be acidic.