Zinc Hydroxide Precipitation

ZnSO₄ + 2NaOH → Zn(OH)₂↓ + Na₂SO₄

Overview

Zinc sulfate reacts with sodium hydroxide to form a white gelatinous precipitate of zinc hydroxide (Ksp = 3.0 × 10⁻¹⁷). Zn(OH)₂ is amphoteric, dissolving in excess NaOH to form the zincate ion [Zn(OH)₄]²⁻. This amphoteric behavior is a diagnostic test for zinc in qualitative analysis.

Participants

Role	Substance	Coefficient	State
Reactant	Zinc Sulfate ZnSO₄	1	(aq)
Reactant	Sodium Hydroxide NaOH	2	(aq)
Product	Sodium Sulfate Na₂SO₄	1	(aq)

Everyday Example

Calamine lotion contains zinc compounds that form protective precipitates on skin, soothing itching from insect bites and rashes.

Industrial Importance

Zinc hydroxide precipitation is used in zinc recovery from wastewater, in calamine lotion production, and as a precursor to zinc oxide.

Properties

Type: Precipitation
Reversible: No
Energy: Exothermic
ΔH: -38.0 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 Zinc Hydroxide Precipitation?

The balanced equation is: ZnSO₄ + 2NaOH → Zn(OH)₂↓ + Na₂SO₄.

What type of reaction is Zinc Hydroxide Precipitation?

Zinc Hydroxide Precipitation is a precipitation reaction.

Is Zinc Hydroxide Precipitation exothermic or endothermic?

Zinc Hydroxide Precipitation is exothermic (releases energy). The enthalpy change (ΔH) is -38.0 kJ/mol.