CuCl2+NaOH

Here’s what happens when CuCl2 is treated with NaOH in aqueous solution:

• With just enough NaOH:

  • Reaction: CuCl2(aq) + 2 NaOH(aq) → Cu(OH)2(s) + 2 NaCl(aq)
  • Observations: A blue precipitate of Cu(OH)2 forms.

• With excess NaOH (copper(II) hydroxide dissolves):

  • Reaction: Cu(OH)2(s) + 2 OH−(aq) → [Cu(OH)4]2−(aq)
  • In salt form: Na2Cu(OH)4
  • Observations: The blue precipitate dissolves to give a deep blue solution.

• Net ionic view (in presence of excess NaOH): Cu2+ + 4 OH− → [Cu(OH)4]2−

• Overall equation with excess NaOH: CuCl2(aq) + 4 NaOH(aq) → Na2Cu(OH)4 + 2 NaCl(aq)

Notes:

• Cu(OH)2 is amphoteric and dissolves in excess base to form the tetrahydroxocuprate(II) complex [Cu(OH)4]2−.
• Color changes: CuCl2 solution is blue-green; Cu(OH)2 precipitate is blue; [Cu(OH)4]2− solution is deep blue.