CaCO3 Equivalent Weight

Establishes calcium carbonate as the common reference for alkalinity because one mole weighs 100 g and neutralizes 2 moles of hydrogen ion, giving the standard 50 g/eq basis used to express concentrations as mg/L as CaCO3.

$$E{W}_{CaC{O}_3}=\frac{MW}{n}=\frac{100g/mol}{2eq/mol}=50g/eq$$

Variables

Symbol	Meaning	Unit
$E{W}_{CaC{O}_3}$	equivalent weight of calcium carbonate	g/eq
MW	molecular weight of CaCO3	g/mol
n	moles of H+ neutralized per mole (valence)	eq/mol

Worked example

One mole of CaCO3 weighs 100 g and neutralizes 2 moles of H+, so 100 divided by 2 equals 50 g/eq. This gives the relation 50 mg/L as CaCO3 equals 1 meq/L.

---

Part of The Blueprint of Water