Rhodium oxide

Uses

Rh2O3 is used to make rhodium metal and its various salts. Also, the oxide is a catalyst for hydrogenation.

Preparation

Rhodium sesquioxide is obtained by heating rhodium metal to red heat in air.
4Rh + 3O2 → 2Rh2O3
Alternatively, Rh2O3 may be prepared by igniting rhodium nitrate, Rh(NO3)3.
Treating the sesquioxide with alkali first forms a yellow precipitate of pentahydrate, Rh2O3•5H2O, soluble in acid and excess alkali. In excess alkali a black precipitate of trihydrate, Rh2O3•3H2O is obtained. The trihydrate is insoluble in acids.

Chemical Properties

Rhodium oxide is YELLOW POWDER

Physical properties

Gray crystalline solid or amorphous powder; corundum-type structure; density 8.20 g/cm³; decomposes at about 1,100 to 1,150°C; insoluble in water, acids, or aqua regia.
The pentahydrate Rh₂O₃?5H₂O is a yellow precipitate; soluble in acids; partially dissolves in hot water; ignites to form anhydrous oxide.
The trihydrate Rh₂O₃?3H₂O is a black precipitate; insoluble in acids.

Uses

Use in the catalytic converters of automobiles. It is also used as an industrial catalyst in the manufacturing of chemical intermediates such as oxo-alcohols, as well as nitric acid and ethanoic (acetic) acid production. It is also an area of interest for new capacitor electrode material researchers, dynamic random access memory (DRAMs) and non volatile random access memories (FeRAMs) makers.

Uses

RH₂o₃ is used to make rhodium metal and its various salts. Also, the oxide is a catalyst for hydrogenation.

Production Methods

Rhodium(III) oxide, Rh2O3, can be prepared by heating the finely divided metal or its nitrate in air or O2. The rhodium(IV) oxide is also known. Rhodium trihydroxide may be precipitated as a yellow compound by adding the stoichiometric amount of KOH to a solution of RhCl3. The hydroxide is soluble in acids and excess base. When the freshly precipitated Rh(OH)3 is dissolved in HCl at a controlled pH, a yellow solution is first obtained in which the aquochloro complex of Rh behaves as a cation.

Flammability and Explosibility

Not classified