Tollen's Test (Silver Mirror)

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

Aperçu

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

Rôle Substance Coefficient État
Produit Water H₂O 1 (l)
Produit Silver Ag 2 (s)
Produit Ammonia NH₃ 4 (aq)

Exemple du quotidien

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

Importance industrielle

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

Propriétés

Type
Redox
Réversible
Non
Énergie
Exothermique
ΔH
-135,0 kJ/mol

Réactions associées

Iron(II) to Iron(III) Oxidation by Oxygen Bleaching with Sodium Hypochlorite Copper Reduction of Silver Ion Aqua Regia Dissolving Gold Cerium(IV) Reduction by Iron(II) Chlorine Oxidation of Bromide Copper Oxidation by Nitric Acid Hypochlorite Oxidation of Hydrogen Peroxide Hydrogen Peroxide as Oxidizing Agent (Acidic) Displacement of Hydrogen from Acid by Magnesium

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.