Copper

Copper metal dissolves in hot concentrated sulphuric acid forming Cu(II) ions and hydrogen, H₂. In water, Cu(II) is present as the complex ion [Cu(H₂O)₆]²⁺ [8].

Cu(s) + 2 H₂SO₄(aq) Cu²⁺(aq) + SO₄²⁻(aq) + H₂(g) + SO₂(g) + 2 H₂O(l)

Copper metal also dissolves in dilute or concentrated nitric acid, HNO3.

3 Cu(s) + 2 NO₃⁻(aq) + 8 H⁺(aq) 3 Cu²⁺(aq) + 2 NO(g) + 4 H₂O(l)

Copper metal is stable in air under normal conditions. When heated until red hot, copper metal and oxygen react to form Cu₂O.

4 Cu(s) + O₂(g) 2 Cu₂O(s)

Copper(II)ions are precipitated by ammonia:

[Cu(H₂O)₆]²⁺(aq) [blue] + 2 NH₃(aq) [Cu(OH)₂(H₂O)₄](s) [blue] + 2 NH₄⁺(aq)

The precipitate dissolves in excess amonia.

[Cu(OH)₂(H₂O)₄](s) + 4 NH₃(aq) [Cu(NH₃)₄]²⁺(aq) [royal blue] + 2 H₂O(l) + 2 OH⁻(aq)

Cu(II) is precipitated by carbonate:

[Cu(H₂O)₆]²⁺(aq) [blue] + CO₃²⁻(aq) CuCO₃(s) [blue] + 6 H₂O(l)

Metallic copper metal reacts with the halogens forming corresponding dihalides.

Cu(s) + F₂(g) CuF₂(s) [white]
Cu(s) + Cl₂(g) CuCl₂(s) [yellow-brown] [8]
Cu(s) + Br₂(g) CuBr₂(s) [black] [8]


Cu(II) forms yellow complexes with 4 Cl⁻. The complex looks green to bluish green, due to the mixture with the blue aqua complex [8]:

[Cu(H₂O)₆]²⁺(aq) [blue, octahedral] + 4 Cl⁻(aq) [CuCl₄]²⁻(aq) [yellow, tetrahedral] + 6 H₂O(l)


Cu(II) is precipitated by Br⁻, forming a black solid [8]:

Cu²⁺(aq) + 2 Br⁻(aq) CuBr₂(s)


Cu(II) is reduced to Cu(I) and precipitated by I⁻ [8]:

2[Cu(H₂O)₆]²⁺(aq) [blue, octahedral]) + 4 I⁻(aq) 2 CuI(s) [white] + I₂(aq) + 6 H₂O(l)

Cu(II) is precipitated by hydroxide. Concentrated hydroxide will dissolve the precipitate:

[Cu(H₂O)₆]²⁺(aq) [blue] + 2 OH⁻(aq) Cu(OH)₂(H₂O)₄(s) [light blue] + 2 H₂O(l)
2 Cu(OH)₂(s) [light blue] + 3 OH⁻(aq) [Cu(OH)₄]²⁻(aq) [blue] + [Cu(OH)₃]⁻(aq) [blue]

Copper is oxidized by Hg(II)

Hg²⁺(aq) + Cu(s) Hg(l) + Cu²⁺(aq)


Copper(II) is reduced by iron and zinc

3 Cu²⁺(aq) + 2 Fe(s) 3 Cu(s) + 2 Fe³⁺(aq)
Cu²⁺(aq) + Zn(s) 3 Cu(s) + Zn²⁺(aq)

Copper(II) is precipitated by sulfide in 0.4 M hydrochloric acid

Cu²⁺(aq) + H₂S(aq) CuS(s) + 2 H⁺(aq)

Copper(II) forms a hexaqua complex with water. The complex is slightly acidic, due to hydrolysis [8]

[Cu(H₂O)₆]²⁺(aq) + H₂O(l) [Cu(H₂O)₅(OH)]⁺(aq) + H₃O⁺(aq)

Method 3500-Cu C Inductively Coupled Plasma Method [1]. A portion of the sample is digested in a combination of acids. The digest is aspirated into an 8,000 K argon plasma where resulting light emission is quantified for 30 elements simultaneously.

Method limit of detection in water = 0.002 mg/L
Method limit of detection in soil = 1.00 mg/kg