Question

Question #ab4a2

Answer 1

`"pH" = 4.77`

Explanation:

The pH of a solution is nothing more than a measure of its concentration of hydrogen ions, `"H"^(+)`, which you'll sometimes see referred to as hydronium cations, `"H"_3"O"^(+)`.

More specifically, the pH of a solution is calculated by taking the negative log base `10` of the concentration of hydrogen ions

`color(blue)(|bar(ul(color(white)(a/a)"pH" = - log(["H"^(+)])color(white)(a/a)|)))`

The problem already provides you with the concentration of hydrogen ions, so plug this into the equation to find

`"pH" = - log(1.7 * 10^(-5)) = color(green)(|bar(ul(color(white)(a/a)4.77color(white)(a/a)|)))`

Notice that because the pH is calculated using a negative log, a higher concentration of hydrogen ions will result in a lower pH.

In fact, the pH of pure water at room temperature is equal to `7` because pure water has

`["H"^(+)]_"pure water" = 1.0 * 10^(-7)"M" " "` and `" "["OH"^(-)]_"pure water" = 1.0 * 10^(-7)"M"`

Your solution has a higher concentration of hydrogen ions, which is why the pH if lower than `7`. This corresponds to an acidic solution.