The reaction sequence shows the conversion of copper (Cu) to different copper compounds: copper oxide (CuO), copper(II) chloride (CuCl2), copper(II) hydroxide (Cu(OH)2), and then finally back to copper oxide (CuO).

Cu ➡️ CuO (copper to copper oxide)CuO ➡️ CuCl2 (copper oxide to copper(II) chloride)CuCl2 ➡️ Cu(OH)2 (copper(II) chloride to copper(II) hydroxide)Cu(OH)2 ➡️ CuO (copper(II) hydroxide to copper oxide)