![]() ![]() Try not to transfer the blue precipitate onto the litmus paper: that will result in some loss of copper, and a possibly false blue on the litmus paper. After a blue precipitate is formed, periodically test the acidity of the solution by dipping your stirring rod into the solution and touching it to red litmus paper.Add the NaOH solution dropwise to the copper solution. Be careful in handling NaOH, for it is a strong base which will sting if it contacts the skin.Keep the mixtures in the hood until after you add the 10 ml of distilled water after completely dissolving the copper. It is important to carry out this step in the fume hood because the brown NO 2 gas is an irritant. ![]() If some copper remains undissolved by the time the production of gas is finished, then put the beaker on the hot plates in the hoods to hasten the reaction.Be careful with the nitric acid: like other strong acids, it will sting if you get it on your skin and can damage clothing unlike most other acids, it will also stain the affected area yellow.Use about 4-5 ml of concentrated HNO 3 solution.That's OK: use the pieces that we provide. The pieces of wire are closer to 0.50 g than 0.35 g. Obtain a piece of copper wire and weigh it to the nearest 0.01 g.ProcedureI won't go over the procedure in step-by-step detail, but I will stress some points of safety and (in bold) some places where our procedure differs from that in the lab packet. 2+ (aq) + Zn (s) -> Cu (s) + Zn 2+ (aq) + 6 H 2O (aq)Īt the same time, some of the zinc metal, which is present in excess, reduces hydronium ions to H 2. We have seen this reaction before in the copper chloride lab). Finally, zinc metal reduces the hydrated copper (II) ion back to metallic copper while itself turning being oxidized to zinc (II) ions.Copper oxide dissolves in acid, regenerating the copper (II) ion, which once again binds to water.Heating copper hydroxide produces copper oxide, CuO, a black solid.As a result, hydroxide ion can displace water from the copper (II) ion, yielding copper hydroxide, Cu(OH) 2, a blue precipitate. Hydroxide ion (OH -) binds to the copper (II) ion even more strongly than does water.The physical change you should observe is the copper-colored metal vanishing as the solution turns blue (from 2+, the hexaaquacopper ion) and a brown gas (NO 2) is evolved. ![]() Actually, the nitrate ion oxidizes the copper metal to copper (II) ion while itself being transformed to NO 2 gas in the process the copper (II) ion then binds to six water molecules. ![]()
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