November 3rd, 2009
Lab Report #3: Copper Cycle
The purpose of the experiment is to cycle solid copper through a series of five reactions. At different stages of the cycle, copper was present in different forms. First reaction involves reaction between the copper and nitric acid, and copper changed from elemental state to an aqueous. The second reaction converted the aqueous Cu2+ into the solid copper (2) hydroxide. In the third reaction Cu(OH)2 decomposed into copper 2 oxide and water when heated. When solid CuO reacted with sulfuric acid, the copper returned to solution as an ion (Cu2+). The cycle of reactions was completed with the reaction where elemental copper was regenerated by Zn and Cu exchanging states in acidic solution.
Reaction 1: Mass of Copper=0.503g
The solution turned green, as well as brown gas evolved, and small particles were moving around at the bottom of the flask, when Nitric acid was added. While slowly swirling the flask, the solution turned blue and Cu completely dissolved upon the completion of the reaction. Reaction 2: The solution formed blue precipitate and thickened when 3.0 M of NaOH was added. Reaction 3: When the solution was heated up the blue color of CO(OH)2 started darkening and after a while turned black CuO settled on the bottom of the flask. Reaction 4: When 15 ml of 6.0 M H2SO4 was added to the flask, the black CuO precipitate completely went away and the solution turned turquoise color. Reaction 5: When 2.001 g of mesh Zn was added to the solution the solution started producing lots of bubbles, H2 gas had evolved, and brown precipitate formed. Blue solution became colorless, and hot. After decanting the liquid the Cu was transferred to porcelain dish and the mass of Cu was determined=0.494g
Reaction 1: 12HNO3 (aq) + 5Cu (s) + 2O2 (g) → 3Cu(NO3)2 (aq) + 6H2O (l) + 2NO2 (g) Type of the reaction: Redox
Net ionic reaction: See attachment on the back for the net...