Question Video: Selecting the Best Choice of Aqueous Solution and Electrode For Electroplating a Key With Copper Chemistry • 10th Grade

A student electroplates a key with copper. What aqueous solution and electrode would be the best choices for this experiment? [A] H₂SO₄(aq) and a graphite electrode [B] H₂SO₄(aq) and a platinum electrode [C] NaOH(aq) and a copper electrode [D] CuSO₄(aq) and a graphite electrode [E] CuSO₄(aq) and a copper electrode


Video Transcript

A student electroplates a key with copper. What aqueous solution and electrode would be the best choices for this experiment? (A) H2SO4 aqueous and a graphite electrode. (B) H2SO4 aqueous and a platinum electrode. (C) NaOH aqueous and a copper electrode. (D) CuSO4 aqueous and a graphite electrode. (E) CuSO4 aqueous and a copper electrode.

Electroplating involves the use of an electrolytic cell to deposit a thin layer of metal onto another metal surface. An electrolytic cell needs a power supply. In this experiment, a simple cell is used to provide the direct current electricity. Our simple cell has a positive terminal and a negative terminal. The positive terminal is called the anode. And at the anode, we would expect to find a source of the metal that is going to provide the plating.

In this scenario, the metal that is providing the plating is copper. So in this experiment, the anode needs to be an electrode made from a piece of pure copper. At this electrode, copper two plus ions will be produced. Copper atoms from the anode will leave two electrons behind on the anode, and they will enter the solution as copper two plus ions. The anode is therefore the site of oxidation here, and the electrons will flow from the anode to the cathode, which is the negative electrode.

In order to plate the key, which is placed at the cathode in this circuit, with copper, we need copper ions to move through the solution and become copper atoms again at the cathode. Since we need a copper electrode to maintain the concentration of copper ions in the solution, we can reject any answers that suggest any other electrode should be used. Answers (A), (B), and (D) are therefore not correct. Graphite is a form of carbon, and it won’t provide any copper ions at all. Platinum is a completely inert metal, and it won’t provide ions either.

The aqueous solution in the electrolytic cell must contain dissolved copper ions. These copper two plus ions will move to the cathode where they will gain two electrons and become copper atoms again, plating the key. This is the site of reduction. Since the solution must contain copper two plus ions, we can reject answer (C). In answer (C), we see a solution of sodium hydroxide. Aqueous sodium hydroxide will contain aqueous sodium ions and aqueous hydroxide ions. These can be written as Na+ (aq) and OH− (aq). Aqueous sodium hydroxide will not yield any copper two plus ions, so it’s not the right answer here. Aqueous copper sulfate or CuSO4 (aq) does yield aqueous copper two plus ions. Answer (E) is the correct answer as we have the correct solution and the correct electrode.

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.