What is the concentration of HCl if its pH is 3?

Apr 29, 2018

${10}^{- 3} \text{ M}$

Explanation:

To find the concentration of something that dissociates into ${H}^{+}$ and something else from the pH, we use the formula:

${10}^{- p H}$

So this becomes:

${10}^{- 3} \text{ M}$ $\quad$(M stands for molar)

Apr 30, 2018

${10}^{-} 3 \setminus \text{M"=0.001 \ "M}$

Explanation:

The $\text{pH}$ of an aqueous solution is given by the equation,

$\text{pH} = - \log \left[{H}^{+}\right]$

• $\left[{H}^{+}\right]$ is the hydrogen ion concentration in terms of molarity

The dissociation equation for hydrochloric acid is:

$H C l \left(a q\right) \to {H}^{+} \left(a q\right) + C {l}^{-} \left(a q\right)$

So, one mole of hydrochloric acid contains one mole of hydrogen ions.

Therefore, the hydrogen ion concentration will be,

$3 = - \log \left[{H}^{+}\right]$

$\left[{H}^{+}\right] = {10}^{-} 3 \setminus \text{M}$

$= 0.001 \setminus \text{M}$