Question

Today in class we did the "gold penny" experiment, where we put metallic zinc and a penny in a zinc chloride1Msolution at100∘C, which caused the penny to turn silver as the zinc coated it. Then, we held the penny to a flame to form brass. I know this is a redox reaction where the zimc is being reduced, but I am confused about the details. What is the exact reaction that goes on? I think the zinc is being reduced into metallic form, and the copper is oxidized. However, I am confused about the specifics - do the ClX− ions re-form ZnClX_2 with the metallic Zn? Or do they stay with the copper after oxidizing it? Sorry if this is simple or obvious - I am 14 years old and just started my first chemistry class. I found this video on a similar reaction today: ?

Answer 1

In the "gold penny" experiment, a redox reaction plates zinc on a penny and then heating forms brass. Zinc metal is oxidized to Zn²+ while Cu²+ ions are reduced to metallic copper. Chloride ions remain in solution throughout the process.

Step-by-step explanation:

The "gold penny" experiment involves a redox reaction where zinc is deposited on a penny in a process known as plating. When the penny, which is composed of copper, is heated in a flame after being coated with zinc, a layer of brass is created due to the formation of an alloy of copper and zinc.

The initial reaction in this process involves zinc metal being oxidized to form Zn²+ (aq) ions, while Cu²+ (aq) ions are reduced to form metallic copper. This reaction can be represented by the equation Zn(s) + Cu²+ (aq) → Zn²+ (aq) + Cu(s). The chloride ions (Cl-) from the zinc chloride solution do not form a new compound with the zinc, nor do they stay with the copper; instead, they remain in solution and maintain the charge balance.