Strong Acid pH Calculator

Calculate the pH of strong acid solutions from concentration and stoichiometric acidity. Instantly compute pH, pOH, and ion concentrations.

M

Concentration of the strong acid in mol/L

Number of H+ ions per molecule (1 for HCl, 2 for H₂SO₄, 3 for H₃PO₄)

Select the strong acid type

Results

pH Value

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pOH Value

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[H⁺] Concentration

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[OH⁻] Concentration

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Frequently Asked Questions

What is pH and how is it calculated?

pH is a measure of acidity or alkalinity of a solution. It's calculated as pH = -log₁₀([H⁺]), where [H⁺] is the hydrogen ion concentration in mol/L.

How do strong acids differ from weak acids in pH calculation?

Strong acids dissociate completely in water, so [H⁺] = n × C, where n is stoichiometric acidity and C is concentration. Weak acids require equilibrium calculations.

What is stoichiometric acidity (n)?

Stoichiometric acidity is the number of H⁺ ions each acid molecule can donate. HCl has n=1, H₂SO₄ has n=2, and H₃PO₄ has n=3.

What is the relationship between pH and pOH?

At 25°C, pH + pOH = 14.00. This relationship comes from the water autoionization constant (Kw = 1.0 × 10⁻¹⁴).

Which acids are considered strong acids?

The common strong acids are HCl, HNO₃, H₂SO₄, HBr, HI, and HClO₄. These acids completely ionize in aqueous solution.

Can pH be negative?

Yes, pH can be negative for very concentrated strong acid solutions. For example, 10 M HCl has a pH of approximately -1.

How accurate are these pH calculations?

These calculations assume complete dissociation, 25°C temperature, and ignore activity effects. They're highly accurate for dilute solutions but less precise for very concentrated solutions.

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