What is the pH of a .001 M solution of HCl?

1 Answer
Jan 8, 2016

"pH" = 3

Explanation:

Hydrochloric acid, "HCl", is a strong acid, which means that it dissociates completely in aqueous solution to form hydronium ions, "H"_3"O"^(+), and chloride anions, "Cl"^(-), in a 1:1 mole ratio.

This tells you that every mole of hydrochloric acid will dissociate to produce one mole of hydronium ions and one mole of chloride anions in aqueous solution.

http://wps.prenhall.com/wps/media/objects/476/488316/ch14.htmlhttp://wps.prenhall.com/wps/media/objects/476/488316/ch14.html

The balanced chemical equation looks like this

"HCl"_text((aq]) + "H"_2"O"_text((l]) -> "H"_3"O"_text((aq])^(+) + "Cl"_text((aq])^(-)

As you know, the pH of a solution is simply a measure of the concentration of hydronium ions.

color(blue)("pH" = - log(["H"_3"O"^(+)]))

So, if you get one mole of hydronium ions for every one mole of hydrochloric acid, you can say that

["H"_3"O"^(+)] = ["HCl"] = "0.001 M"

This means that the pH of the solution will be

"pH" = - log(0.001)

"pH" = color(green)(3)