Copper (II) oxide

 

Copper (II) oxide
aka cupric oxide, black copper oxide

Chemical formula	CuO
OTP appearance	black powder
Molar Mass(g/mol)	79.545
Density(g/cc)	6.315
Melting Point(°C)	1326
Boiling Point(°C)	2000
Solubility in water(g/L)	0
NFPA 704	0 2 1

Uses

Primary

• Primary intermediate for copper and bronze

Other

• Catalyst
• Precursor to cuperammonium for the production of rayon
• Glass polishing
• Component of copper-aluminum thermite
• P-type semiconductor

Natural occurrence

• Occurs naturally as the rare mineral tenorite

Production

Extraction

• Calcining malachite or azurite. (~290°C)

Synthesis

Heating copper to 300°C in air produces CuO.

1. Gather 100ubm of fine copper grains
2. Heat over a flame in a shallow thin-walled crucible
3. Repeat
   1. Stir the grains over a steady, strong heat until they become a uniform dark grey or black

      NB: the stirring is vital, or the copper oxide "crust" will prevent air from reaching the inner mass of copper, and solidify the entire mass into a single lump which will be hard to manipulate

   2. Grind filings thoroughly in a mortar and pestle

      NB: this is to crack off any CuO "skin", exposing new copper on the surface of the grain

   3. Weigh the filings.
4. Until filings weigh close to 125ubm (Cu: ~64g/mol, CuO ~80g/mol
5. The filings are predominantly copper (II) oxide

As an example, 325mesh (44μm) copper powder will accumulate 10% weight in about 30 minutes in a crucible on a gas stove. The coarser the powder, the smaller the surface area, thus the less oxygen can react with the powder, and the less mass it can gain.

See Also

• Lee, Shao-Kuan; Hsu, Hsiu-Ching; Tuan, Wei-Hsing (2016) "Oxidation Behavior of Copper at a Temperature below 300 °C and the Methodology for Passivation"
  Materials Research 19(1) 
  DOI:10.1590/1980-5373-MR-2015-0139