H⁺ Concentration Calculator
Calculate the molarity of Hydrogen protons from pH, pOH, or Hydroxide concentration.
Supports scientific notation (e.g. 1.5e-5)
Proton Density Visualizer
More dots = More Acidic = Lower pH
The Chemistry of Acidity
The concentration of Hydrogen ions is the master variable in chemistry. It determines whether a liquid is a life-sustaining water or a metal-dissolving acid.
Calculating [H⁺]
While pH is convenient for labels, Molarity (M) is what you need for stoichiometry and reaction rates.
The Logarithmic Scale
Our brains think linearly (1, 2, 3), but chemistry works exponentially.
- x 10Each 1 point decrease in pH (e.g., 7 to 6) means the acid is 10 times more concentrated.
- x 100A 2 point drop (e.g., 7 to 5) means 100 times more protons.
- x 1MGoing from neutral water (pH 7) to stomach acid (pH 1) increases concentration by 1,000,000 times!
pH to Molarity Conversion Table
| pH | [H⁺] in Scientific Notation | [H⁺] Decimal (Molarity) | Common Example |
|---|---|---|---|
| 0 | 1 × 100 M | 1.0 M | Battery Acid |
| 2 | 1 × 10-2 M | 0.01 M | Lemon Juice |
| 4 | 1 × 10-4 M | 0.0001 M | Tomato Juice |
| 7 | 1 × 10-7 M | 0.0000001 M | Pure Water (Neutral) |
| 10 | 1 × 10-10 M | 0.0000000001 M | Milk of Magnesia |
| 14 | 1 × 10-14 M | 0.00000000000001 M | Drain Cleaner |
Enzyme Activity
Biological enzymes are folded proteins. Their shape depends on the exact concentration of H+ ions (Molarity) around them. Even a slight change in [H+] can denature proteins, stopping critical life functions.
Dilution Logic
If you dilute an acid by 10x with water, the [H+] decreases by 10x, so the pH goes UP by 1. If you dilute it 100x, pH goes UP by 2. This is why washing acid spills with water is effective.
Safety
Our skin is slightly acidic (pH 5.5). Strong acids (High [H+]) donate protons so aggressively that they break down cellular structures (chemical burns). Alkalis (Low [H+]) are equally dangerous as they saponify fats.
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Frequently Asked Questions
What is [H⁺] Concentration?
It refers to the Molarity (moles per liter) of hydrogen ions (H+) in a solution. In reality, these protons bond with water molecules to form hydronium ions (H3O+), but chemists use [H+] for simplicity.
How do I calculate [H⁺] from pH?
The formula is the reverse of the pH definition: [H+] = 10-pH. For example, if pH is 5, then [H+] = 10-5 = 0.00001 M.
What is Molarity (M)?
Molarity is the standard unit of concentration in chemistry. 1 M means there is 1 mole of solute (approx 6.022 × 1023 particles) per liter of solution.
What is the [H⁺] of pure water?
At room temperature (25°C), pure water has a pH of 7, which means [H+] = 10-7 M (or 0.0000001 mol/L). This equal balance of H+ and OH- is why water is neutral.
How do I find [H⁺] from pOH?
First, find the pH using pH = 14 - pOH. Then use the standard formula [H+] = 10-pH to find the concentration.
Why does low pH mean high concentration?
Because the pH scale is logarithmic and negative. A lower number (like 1) means 10-1 (0.1 M), while a higher number (like 14) means 10-14 (a very tiny number). Think of it like a discount: a bigger 'negative' exponent means a smaller value.
Can [H⁺] be greater than 1 M?
Yes. Highly concentrated strong acids (like 12M Hydrochloric Acid) have molarities much greater than 1. This results in a negative pH (e.g., pH of 2M HCl is approx -0.3).
How do I calculate [H⁺] from [OH⁻]?
Use the ion product constant of water (Kw = 1.0 × 10-14). The formula is [H+] = Kw / [OH-].
What is Kw?
Kw is the auto-ionization constant of water. Even pure water naturally splits slightly into ions. At 25°C, the product of [H+] and [OH-] is always constant at 1.0 × 10-14.
What is the difference between H+ and H3O+?
They represent the same acidity concept. A bare proton (H+) is too reactive to exist freely in water; it instantly attaches to H2O to form Hydronium (H3O+). However, equations typically use [H+] for brevity.
Why use scientific notation?
Because concentrations can be incredibly small (e.g., 0.00000000000001 M for pH 14). Scientific notation (e.g., 1.0 × 10-14) makes these numbers much easier to read and allows for quicker mental math comparisons.
Is [H+] temperature dependent?
Yes! The Kw of water changes with temperature. At 100°C (boiling water), the neutral pH is actually around 6.14, meaning the [H+] concentration is higher than at room temperature.
What represents a 10x change in acidity?
Moving 1 unit on the pH scale represents a 10x change in [H+]. Moving 2 units represents a 100x change. This is the power of the logarithmic scale.
How do I measure [H+] directly?
You cannot count atoms directly. You typically measure pH using a pH meter or litmus paper, and then mathematically convert that value back to [H+] using this calculator.
Are [H+] and acidity the same thing?
Technically, yes. Acidity is defined by the concentration of H+ ions. The higher the [H+], the more acidic the solution, the more sour it tastes, and the more corrosive it is.