By Contributing Writer — Updated Aug 30, 2022
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A solution’s concentration describes how much solute is dissolved per unit volume. While molarity (mol L⁻¹) counts moles, normality (N) counts chemical equivalents—essentially the number of reactive units a solute can provide. For example, sulfuric acid (H₂SO₄) donates two protons, so a 1 M H₂SO₄ solution has a normality of 2 N.
Below is a concise, step‑by‑step method to convert a normality value into the mass of solute in grams. We’ll use 240 mL of a 2.5 N H₂SO₄ solution as a running example.
Refer to a reliable periodic table to find the atomic masses: H = 1.01 g mol⁻¹, S = 32.07 g mol⁻¹, O = 16.00 g mol⁻¹.
Add the weights of all atoms in the formula: (2 × 1.01) + 32.07 + (4 × 16.00) = 98.09 g mol⁻¹.
Divide the molar mass by the number of protons released upon dissociation. For H₂SO₄, the reaction is H₂SO₄ → 2 H⁺ + SO₄²⁻, so the equivalent mass is 98.09 / 2 = 49.05 g equiv⁻¹.
240 mL equals 0.240 L.
Multiply normality, equivalent mass, and volume: 2.5 N × 49.05 g equiv⁻¹ × 0.240 L = 29.34 g (≈ 29.4 g).
Follow this routine for any normality‑to‑grams conversion, and you’ll achieve precise, reproducible results—critical for laboratory work, industrial processes, and educational labs alike.
