Copper Sulfide Precipitation

CuSO₄ + Na₂S → CuS↓ + Na₂SO₄

Overview

Copper sulfate reacts with sodium sulfide to form a black precipitate of copper(II) sulfide (Ksp = 1.3 × 10⁻³⁶). CuS is one of the most insoluble compounds known. The jet-black precipitate forms instantly and is used to identify Cu²⁺ ions in systematic qualitative analysis.

Participants

Role	Substance	Coefficient	State
Reactant	Copper(II) Sulfate CuSO₄	1	(aq)
Product	Sodium Sulfate Na₂SO₄	1	(aq)

Everyday Example

The black tarnish on copper pots exposed to sulfur-containing foods (eggs, garlic) is related to copper sulfide formation.

Industrial Importance

Sulfide precipitation is used in mining wastewater treatment to remove heavy metals. CuS (covellite) is also a naturally occurring copper ore mineral.

Properties

Type: Precipitation
Reversible: No
Energy: Exothermic
ΔH: -84.0 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) Calcium Sulfate Precipitation (Gypsum) Chromium(III) Hydroxide Precipitation

Frequently Asked Questions

What is the equation for Copper Sulfide Precipitation?

The balanced equation is: CuSO₄ + Na₂S → CuS↓ + Na₂SO₄.

What type of reaction is Copper Sulfide Precipitation?

Copper Sulfide Precipitation is a precipitation reaction.

Is Copper Sulfide Precipitation exothermic or endothermic?

Copper Sulfide Precipitation is exothermic (releases energy). The enthalpy change (ΔH) is -84.0 kJ/mol.