If you are working in a chemical or other scientific laboratory, you may need to use a pH meter to find the
solution is acidic or basic.
When pH or pOH of solution is known, we can readily calculate concentrations of hydronium ion
(H_{3}O^{+}) or hydroxyl ion (OH^{-}) using the pH equation. Also, in this online pH calculator,
you have to just substitute pH or pOH value and it will give you what is the H_{3}O^{+} ion concentration of
aqueous solution. Also, several examples are explained with each step of calculation at the end of this tutorial.

Sometimes, H_{3}O^{+} is denoted as H^{+} and we also use H^{+} term instead of H_{3}O^{+} term.

There are two calculators in this online calculator.

- Calculator of pH to H
^{+}concentration - Calculator of pOH to H
^{+}and OH^{-}concentration

This calculator will give H^{+} concentration in mol dm^{-3}. Ionic product (K_{w} value) of water is taken as 1 * 10^{-14}
mol^{2} dm^{-6}. Therefore, results of this online calculator are very much accurate around 25^{0}C.

Answer

- If you see 'e' in the answer take e = 10, as an example if answer is given as 1e-7, it means 1 * 10
^{-7} - If answer is given as 1.00005e-5, 1.00005e-5 = 1.00005 * 10
^{-5}

This calculator will give H^{+} concentration in mol dm^{-3}. Here also, results of this online
calculator are very much accurate around 25^{0}C.

Answer

Because pH = 1, this solution is a strong acidic solution. We can substitute pH = 1 in pH equation.

- pH = -log[H
^{+}] - 1 = -log[H
^{+}] - [H
^{+}] = 0.1 mol dm^{-3}

Because pH = 13, this solution is a strong basic solution. We can substitute pH = 1 in pH equation.

- pH = -log[H
^{+}] - 13 = -log[H
^{+}] - [H
^{+}] = 1 * 10^{-13}mol dm^{-3}

Because pH + pOH = 14 at 25^{0}C.

- pH + pOH = 14
- 13 + pOH = 14
- pOH = 13

From pOH equation, OH^{-} concentration can be calculated.

- pOH = -log[OH
^{-}] - 1 = -log[OH
^{-}] - [OH
^{-}] = 0.1 mol dm^{-3}

Because pH value is given, we can find the H^{+} concentration directly from pH equation.

- pH = -log[H
^{+}] - 3 = -log[H
^{+}] - [H
^{+}] = 1 * 10^{-3}mol dm^{-3}

Whether acetic acid concentration is given, we cannot get a direct and
easy relationship between acetic acid concentration
and H^{+} ion concentration because acetic acid is a weak acid.

In the answer too, you can see **H ^{+} ion concentration is much lower than acetic acid concentration**.

Questions

If there are two or more acids in a aqueous solution, all of them give H^{+} ions in different amounts (or in concentrations).
So, there is only one H^{+} ion concentration throughout the aqueous solution. So, pH value is uniform throughout the solution.
When, we measure the pH value of acidic solution and calculate H^{+} ion concentration, it indicates the overall H^{+}
concentration of solution. But, you cannot decide individual concentrations of HCl and H_{2}SO_{4} acids.

See pH equation. There are only 2 terms in pH equation, H^{} ion concentration and pH value. There is no term for temperature. So, there is no effect for H^{+} ion concentration when it is calculated from pH value in different temperatures.

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