pH, pOH to H+ Concentration Online Calculator | Example Problems
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 (H3O+) 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 H3O+ ion concentration of aqueous solution. Also, several examples are explained with each step of calculation at the end of this tutorial.
Sometimes, H3O+ is denoted as H+ and we also use H+ term instead of H3O+ term.
There are two calculators in this online calculator.
- Calculator of pH to H+ concentration
- Calculator of pOH to H+ and OH- concentration
Calculator of pH to H+ concentration
This calculator will give H+ concentration in mol dm-3. Ionic product (Kw value) of water is taken as 1 * 10-14 mol2 dm-6. Therefore, results of this online calculator are very much accurate around 250C.
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
Calculator of pOH to H+ and OH- concentration
This calculator will give H+ concentration in mol dm-3. Here also, results of this online calculator are very much accurate around 250C.
Answer
Example problems for calculating H+ concentration when pH or pOH values are known
What is the H+ concentration in an aqueous solution which show pH = 1 ?
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
What are the H+ and OH- concentrations in pH = 13 solution?
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 250C.
- 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
Variation of pH and H+ ion concentration
Aqueous acetic acid solution has the pH value of 3 and concentration of acetic acid is 0.05 mol dm-3. What is the H+ concentration of acetic acid solution?
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
What are the applications of converting pH values to H+ concentration values?
In some chemistry application, pH values will be given to maintain conditions of different processes. In such cases, it is essential to calculate concentrations of chemicals in such situatins. The, we can do a calculation based on the given pH value. Because we can convert pH value to H+ ion concentration and can continue the calcuation to calculate concentrations of other chemicals. Some examples are given below.
- Preparing acetic acid solution which has a pH value of 3
Can I use this calculator for an acid mixture such as HCl and H2SO4?
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 H2SO4 acids.
If I know pH value of aqueous solution and when I calculate H+ ion concentration from pH equation, is it correct for every temperature?
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.