Cu → CuO → CuCl2 → Cu(OH)2 → CuO → Cu → CuSO4 → Cu(OH)

4) Copper reacts with oxygen to form copper(II) oxide. Copper(II) oxide reacts with hydrochloric acid to form copper(II) chloride. Copper(II) chloride reacts with sodium hydroxide to form copper(II) hydroxide. Copper(II) hydroxide decomposes upon heating to copper(II) oxide and water. Copper(II) oxide reacts with hydrogen to form copper and water. Copper reacts with sulfuric acid to form copper(II) sulfate and sulfur dioxide and water. Copper(II) sulfate reacts with sodium hydroxide to form copper(II) hydroxide and sodium sulfate.