# Question 702d7

Oct 27, 2016

Using the formula for $\text{pH}$, "pH" = -log["H"^+]

#### Explanation:

We also have to work out the molarity of the aqueous acid.

Let's look at an example:

Calculate the $\text{pH}$ of a $0.0025$ $\text{M}$ $\text{HCl}$ solution.

${\text{HCl" ("aq") + "H"_2"O" ("l") rarr "H"_3"O"^+ + "Cl}}^{-}$

$\text{HCl}$ is a strong acid and is 100%# ionised in water. Thus, the hydronium ion concentration is $0.0025 \text{M}$.

$\text{pH} = - \log \left(0.0025\right) = - \left(- 2.60\right) = 2.60$