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. See also our pKb Calculator.
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. You might also find our calculate pOH pOH Value useful.