Normality Calculator
Find the normality of a concentrated liquid reagent such as an acid or base. Enter its density, assay (purity) and equivalent weight, and leave the value you want to find blank.
Leave exactly one field blank to solve for it.
How it works
Normality (N) is the number of gram-equivalents of solute per litre of solution. For a concentrated liquid reagent, its normality follows from the label values: N = (10 × density × assay%) ÷ equivalent weight. The factor of 10 converts the density in g/mL and the assay percentage into grams of pure reagent per litre.
Enter any three of normality, density, assay and equivalent weight and leave the fourth blank — the calculator rearranges the formula and solves it. The equivalent weight is the molar mass divided by the number of reactive units (for a monoprotic acid it equals the molar mass; for a diprotic acid it is half the molar mass).
Examples
- Concentrated HCl (density 1.18 g/mL, assay 37%, EW 36.46): N = 10 × 1.18 × 37 / 36.46 ≈ 11.97 N.
- Concentrated H2SO4 (density 1.84, assay 98%, EW 49.04): N = 10 × 1.84 × 98 / 49.04 ≈ 36.8 N.
- Glacial acetic acid (density 1.05, assay 99.7%, EW 60.05): N ≈ 17.4 N.
Frequently asked questions
- What is normality?
- Normality is the concentration expressed as gram-equivalents of reactive species per litre. It equals molarity multiplied by the number of equivalents per mole (protons for an acid, hydroxides for a base, electrons for a redox agent).
- What is equivalent weight?
- Equivalent weight is the molar mass divided by the valence or number of reactive units. HCl provides one proton so its equivalent weight equals its molar mass (36.46); H2SO4 provides two, so its equivalent weight is half its molar mass.
- Where do I find density and assay?
- Both are printed on the reagent bottle. Density (specific gravity) is given in g/mL and the assay or purity as a percentage.
- How is normality related to molarity?
- Normality = molarity × equivalents per mole. For a monoprotic acid the two are equal; for a diprotic acid the normality is twice the molarity.