Calcium Sulfate Precipitation (Gypsum)

Ca(NO₃)₂ + Na₂SO₄ → CaSO₄↓ + 2NaNO₃

Overview

Calcium nitrate reacts with sodium sulfate to precipitate calcium sulfate (Ksp = 4.9 × 10⁻⁵). CaSO₄ is sparingly soluble, not truly insoluble. The dihydrate form (CaSO₄·2H₂O) is gypsum, one of the most important construction materials. Plaster of Paris is the hemihydrate form.

Participants

Role	Substance	Coefficient	State
Reactant	Sodium Sulfate Na₂SO₄	1	(aq)
Product	Calcium Sulfate CaSO₄	1	(s)
Product	Sodium Nitrate NaNO₃	2	(aq)

Everyday Example

Drywall (gypsum board) used in nearly every building contains calcium sulfate dihydrate, produced by similar precipitation chemistry.

Industrial Importance

Gypsum production exceeds 250 million tonnes annually for drywall, plaster, cement, and soil amendment. FGD gypsum from power plants is increasingly important.

Properties

Type: Precipitation
Reversible: No
Energy: Exothermic
ΔH: -8.0 kJ/mol

Related Reactions

Aluminum Hydroxide Precipitation Barium Carbonate Precipitation Barium Sulfate Precipitation Cadmium Sulfide Precipitation (Yellow) Calcium Carbonate Precipitation Calcium Fluoride Precipitation (Fluorite) Calcium Oxalate Precipitation (Kidney Stones) Calcium Phosphate Precipitation (Bone Mineral) Chromium(III) Hydroxide Precipitation Cobalt(II) Hydroxide Precipitation

Frequently Asked Questions

What is the equation for Calcium Sulfate Precipitation (Gypsum)?

The balanced equation is: Ca(NO₃)₂ + Na₂SO₄ → CaSO₄↓ + 2NaNO₃.

What type of reaction is Calcium Sulfate Precipitation (Gypsum)?

Calcium Sulfate Precipitation (Gypsum) is a precipitation reaction.

Is Calcium Sulfate Precipitation (Gypsum) exothermic or endothermic?

Calcium Sulfate Precipitation (Gypsum) is exothermic (releases energy). The enthalpy change (ΔH) is -8.0 kJ/mol.