Tollen's Test (Silver Mirror)

RCHO + 2Ag(NH3)2+ + 2OH− → RCOO− + 2Ag + 4NH3 + H2O

Overview

Tollens' reagent (silver-ammonia complex) is reduced to metallic silver by aldehydes, producing a silver mirror on the test tube walls. The aldehyde is oxidized to a carboxylate. This test distinguishes aldehydes from ketones, as ketones cannot be easily oxidized. It was historically used for mirror manufacturing.

Participants

Role Substance Coefficient State
Product Water H₂O 1 (l)
Product Silver Ag 2 (s)
Product Ammonia NH₃ 4 (aq)

Everyday Example

The silver mirror test creates a beautiful reflective coating on glass, and this chemistry was actually used to make mirrors commercially.

Industrial Importance

Tollens' test is used in organic chemistry for aldehyde identification. Silver mirror manufacturing by chemical reduction is still used for high-quality mirrors.

Properties

Type
Redox
Reversible
No
Energy
Exothermic
ΔH
-135.0 kJ/mol

Related Reactions

Aqua Regia Dissolving Gold Bleaching with Sodium Hypochlorite Cerium(IV) Reduction by Iron(II) Chlorine Oxidation of Bromide Chromate-Dichromate Equilibrium Contact Process SO₂ Oxidation Copper Displaced by Iron Copper Oxidation by Nitric Acid Copper Patina Formation (Verdigris) Copper Reduction of Silver Ion

Frequently Asked Questions

What is the equation for Tollen's Test (Silver Mirror)?
The balanced equation is: RCHO + 2Ag(NH₃)₂⁺ + 2OH⁻ → RCOO⁻ + 2Ag + 4NH₃ + H₂O.
What type of reaction is Tollen's Test (Silver Mirror)?
Tollen's Test (Silver Mirror) is a redox reaction.
Is Tollen's Test (Silver Mirror) exothermic or endothermic?
Tollen's Test (Silver Mirror) is exothermic (releases energy). The enthalpy change (ΔH) is -135.0 kJ/mol.